Adding and reading byte variable from the bit array?

[mpgmike]

The best I can think of is shifting & bit masks. If you want to use bits 2 through 5, create a generic temporary variable to put the interim result. Right shift it to put the 1st needed bit at the 0 position, then AND mask it. The Temp variable will now be %0000 xxxx. Reverse the process for the destination variable using an OR mask first, then left shift it to put the key bits in %xxxx 0000.

SourceVar VAR BYTE
DestVar VAR BYTE
TempVar VAR BYTE

TempVar = (SourceVar >> 2) AND $0F
DestVar = (TempVar << 4) OR $F0

or maybe

DestVar = (SourceVar << 2) AND $F0