How (in conditional formatting) can I ask excel to allow a difference of +,-
..01? For example, A1=12.21 and B1=12.22. I want B1 to turn red if it is
not equal to A1, allow a .01 difference. In this case B1 will not turn red.

If A1=12.21 and (B1=12.23 or B1=12.19), then the cell (B1) will turn red.