I tried compiling that and I get

Symbol not previously defined (INTCON1)

The updated code is as follows:

' Connect analog input to (RA0)
' Connect clocks to PORTB
' PORTB.0 is the Vphase1 clock
' PORTB.1 is the Vphase2 clock
' PORTB.2 is the Hphase1 clock
' PORTB.3 is the Hphase2 clock
' The reset will be connected to a HWPM clock pin #17
' Connect pin 2 from the DB9 connector to PORTC.6
' Have a +5V source ready to touch PORTA.2 to trigger clocking process

include "modedefs.bas"

' Define ADCIN parameters
Define ADC_BITS 8 ' Set number of bits in result
DEFINE OSC 20 ' Sets clock speed to 20Mhz
Define ADC_CLOCK 4 ' Set clock source (3=rc)
Define ADC_SAMPLEUS 50 ' Set sampling time in uS

HPWM 1,64,3600 ' Supposed to send HPWM 3.6KHZ at 25% duty

INTCON1 = %1001000 ' Enable RB0 Interrupt
INTCON.7 = 0 ' Disables global interrupts
TRISA = %11111111 ' Set PORTA to all input
ADCON1 = %00001101 ' Set PORTA analog, except for pin 2
TRISB = %00000000 ' Set PORTB to all output
Pause 500 ' Wait .5 second
Pause 500 ' Wait .5 second

horizpulse var byte
vertpulse var byte
adval var byte ' Create adval to store result

horizpulse = 1 ' Initialize counters, initial states
vertpulse = 1
PORTB.0 = 0
PORTB.1 = 0
PORTB.2 = 1
PORTB.3 = 0

buttonloop:
IF PORTA.2 = 1 then
GOTO vertloop
else
GOTO buttonloop ' Waits for 5V that signals shutter is closed
ENDIF
vertloop:
horizpulse = 1
PORTB.0 = 1
PAUSEUS 139
PORTB.0 = 0
PORTB.1 = 1
PAUSEUS 139
PORTB.0 = 1
PORTB.1 = 0
PAUSEUS 139
PORTB.0 = 0
PAUSEUS 270
vertpulse = vertpulse + 1
IF vertpulse < 512 THEN
GOTO horizloop
ELSE
GOTO buttonloop
ENDIF
horizloop:
INTCON.1 = 0 ' Resets interrupt flag to 0
Resetcheck: ' Loops back to make sure
PAUSEUS 2 ' the PORTB.2 goes low and
IF INTCON.1 = 0 THEN ' PORTB.3 goes high as close
GOTO Resetcheck ' to the external trigger's
ELSE ' rising edge as possible
ENDIF
PORTB.2 = 0
PORTB.3 = 1
PAUSEUS 139
PORTB.3 = 0
PORTB.2 = 1
PAUSEUS 15
ADCIN 0, adval ' A/D 8 bit value from PORTA.0 into adval
SEROUT2 PORTC.6,16416,[BIN8 adval,13,10] ' Output 8 bit word serially to PC from C.6
PAUSEUS 87
horizpulse = horizpulse + 1
IF horizpulse < 784 THEN
GOTO horizloop
ELSE
PAUSEUS 270
GOTO vertloop
ENDIF
END