See my comments in the original thread re word size.

While you are waiting, here is a UDF NOT function:
Code:
Function funNot($dValue,Optional $iWordSize)

   ; Cast result to correct type

   $funNot=CDbl(1)

   	

   ; Calculate the value of all bits set

   If Val($iWordSize) $iWordSize=Val($iWordSize) Else $iWordSize=16 EndIf

   While $iWordSize $iWordSize=$iWordSize-1 $funNot=$funNot*2 Loop

   	

   $funNot=($funNot-1)-$dValue

EndFunction

To use:
Code:
Turn off bit: $x = $x & funNot(64)


If the size of the mask is important, supply the optional word size:
Code:
"The maximum value of an 8 bit word (byte) is: " funNot(0,8)


I've left the default word size set as 16 bits.