Code:
CALC_Checksum1:
    Checksum1 = 0
    WORD_HOLD = 0
    for i = 3 to MAX_LEN
       Word_Hold = Word_Hold + tx_data1(i)
     next 
     Checksum1 = WORD_HOLD.byte0 ^ $FF
    RETURN

CALC_Checksum2:
    Checksum2 = 0
    for i = 3 to MAX_LEN
       Checksum2 = Checksum2 + tx_data1(i)
    next 
    Checksum2 =  Checksum2 // 256
   'Checksum2 = -Checksum2
    RETURN
the above routines i pieced together from other posts here to genereate a checksum for transimitted data packets.

to validate on the received end, do i run the same routine and compare values to see if the checksums are equal?