Thanks for your inquiry.
I suppose, moreover, I'm in need of assistance with the intricacies of the USART registers, interrupts, etc. I've been reading a few posts here regarding "lost" bytes due to buffer overflows. I'd sure love a quick interrupt routine to avoid that problem (maybe parsing the bytes? I dunno?). I'm also interested in a pro reviewing the code and giving a yeah or nay to it, as far as basic functionality. If nay, I'll go back to the drawing board with suggestions-fixes in tow. I certainly don't expect any of you guys to do the project for me, just pro advice for a newbie that's a bit confused. Maybe one of you guys could put the boards through their paces on a simulator? Am I on the right track as far as the commands coming from the pc serial port?
"AxOyLz"
...where x = address 1-256 (8 bit)
After "A", grab next byte
...where y = output 1-24 (8 bit)
After "O", grab next byte
...where z = level 1-100 (8 bit)
After "L", grab next byte
I hope all this gibberish is not confusing to you! Just trying to fly-out my questions rattling in my noodle right now.
Anyhow, after posting the "masterboard" code, I revamped it a bit...hopefully for the better?
Thanks again for your time and advice.

Code:
' MASTERBOARD.BAS

'TO DO: SET ALL REGISTERS AND DEFINES
'       MAYBE AN INTERRUPT ROUTINE FOR SERIAL IN?

Include "modedefs.bas"
define OSC 20           
'DEFINE HSER_RCSTA 18h   ' Set receive register to receiver enabled
'DEFINE HSER_TXSTA 98h   ' Set transmit register to transmitter enabled

TXSTA = %00100100
RCSTA = %10010000

ADCON1 = %00000110
TRISA = %00000000
TRISB = %10000000
TRISC = %00000000
TRISD = %00000000

INTCON = %01000000
PIE1.5 = 1          'USART RX INTERRUPT ENABLE

SerRxOK     var PORTB.4
SerInPin    var PORTC.7
SerOutPin   var PORTC.6
ADRpin      var PORTB.0
ProgLED     var PORTB.7
HrtbtLED    var PORTB.6

Address     var byte
OutPin      var byte
OutLevel    var byte
BoardAdd    var byte
UpdPinLvl   var byte

low Progled
LOW HRTBTLED

Start:
    if Adrpin then
        serin SerInPin,t9600,["A"],boardadd
            IF (boardadd > 0) and (boardadd < 256) THEN
                write 0,boardadd
                high Progled
                    pause 1000
                low progled
                serout seroutpin,t9600,["Board address set to ",boardadd,13,10]
            else        
                serout seroutpin,t9600,["Error: Address ",boardadd," not valid! Please use 1 to 256.",13,10]
            endif
        goto Start
    else
        read 0,boardadd
        IF (BOARDADD = 0) OR (BOARDADD > 256) THEN
            serout seroutpin,t9600,["Board is not addressed. Please set address between 1 and 256.",13,10]
            goto start
        endif
        serin SerInPin,t9600,["A"],address            '1 - 256
            IF ADDRESS <> boardadd THEN
                goto start
            endif    
        serin SerInPin,t9600,["O"],outpin     '1 - 24
            if (outpin = 0) or (outpin > 24) then
                serout seroutpin,t9600,["Error: Output ",outpin," is not valid! Please use 1 to 24.",13,10]
                goto start
            endif 
        serin SerInPin,t9600,["L"],outlevel   '0 = OFF, 5 = 5%, 10 = 10%, ...50 = 50%,...100 = 100% (by 5's)
            if outlevel > 100 then
                serout seroutpin,t9600,["Error: Level ",outlevel," is not valid! Please use 0 to 100 (By FIVES).",13,10]
                goto start
            endif
                                    
        write outpin,outlevel            'Output will match EEPROM location
        read outpin,UpdPinLvl
        serout seroutpin,t9600,["Updated output ",outpin," to level ",UpdPinLvl * 5,13,10]
        select case outpin
            case 1
                serout portA.3,n9600,[UpdPinLvl]    'CAT5 JACK 1, PIN 1
            case 2
                serout portB.1,n9600,[UpdPinLvl]    'CAT5 JACK 1, PIN 2
            case 3
                serout portA.2,n9600,[UpdPinLvl]    'CAT5 JACK 1, PIN 3
            case 4
                serout portB.2,n9600,[UpdPinLvl]    'CAT5 JACK 1, PIN 4
            case 5
                serout portA.1,n9600,[UpdPinLvl]    'CAT5 JACK 1, PIN 5
            case 6
                serout portB.3,n9600,[UpdPinLvl]    'CAT5 JACK 1, PIN 6
            case 7
                serout portE.0,n9600,[UpdPinLvl]    'CAT5 JACK 2, PIN 1
            case 8
                serout portA.5,n9600,[UpdPinLvl]    'CAT5 JACK 2, PIN 2
            case 9
                serout portE.1,n9600,[UpdPinLvl]    'CAT5 JACK 2, PIN 3
            case 10
                serout portA.4,n9600,[UpdPinLvl]    'CAT5 JACK 2, PIN 4
            case 11
                serout portE.2,n9600,[UpdPinLvl]    'CAT5 JACK 2, PIN 5
            case 12
                serout portA.4,n9600,[UpdPinLvl]    'CAT5 JACK 2, PIN 6
            case 13
                serout portC.3,n9600,[UpdPinLvl]    'CAT5 JACK 3, PIN 1
            case 14
                serout portC.2,n9600,[UpdPinLvl]    'CAT5 JACK 3, PIN 2
            case 15
                serout portD.0,n9600,[UpdPinLvl]    'CAT5 JACK 3, PIN 3
            case 16
                serout portC.1,n9600,[UpdPinLvl]    'CAT5 JACK 3, PIN 4
            case 17
                serout portD.1,n9600,[UpdPinLvl]    'CAT5 JACK 3, PIN 5
            case 18
                serout portC.0,n9600,[UpdPinLvl]    'CAT5 JACK 3, PIN 6
            case 19
                serout portD.4,n9600,[UpdPinLvl]    'CAT5 JACK 4, PIN 1
            case 20
                serout portD.5,n9600,[UpdPinLvl]    'CAT5 JACK 4, PIN 2
            case 21
                serout portC.5,n9600,[UpdPinLvl]    'CAT5 JACK 4, PIN 3
            case 22
                serout portD.6,n9600,[UpdPinLvl]    'CAT5 JACK 4, PIN 4
            case 23
                serout portC.4,n9600,[UpdPinLvl]    'CAT5 JACK 4, PIN 5
            case 24
                serout portD.7,n9600,[UpdPinLvl]    'CAT5 JACK 4, PIN 6
        END SELECT
    TOGGLE HRTBTLED             'Flashing pretty damn fast!
endif
goto Start