Sounds like what you're looking for is the DCD operator:
DCD returns the decoded value of a bit number. It changes a bit number (0 - 31) into a binary number with only that bit set to 1. All other bits are set to 0.
B0 = DCD 2 ' Sets B0 to %00000100
So, perhaps something:
Code:
OutBits VAR WORD
  GPA VAR OutBits.BYTE0
  GPB VAR OutBits.BYTE1

Outbits = DCD $E
Henrik.