Workday Func and conditional formatting

[Nick]

Is it possible to use the WORKDAY function inconjunction
with TODAY(), a number and a date in a conditional format.

The following line in an IF statement works fine:-

=IF(WORKDAY(TODAY(),A20)>B20,"TOO MUCH WORK","") where
A20= a number and B20 = a date.

But when I try the following:-

=WORKDAY(TODAY(),A20)>B20 I get a message stating cannot
reference to other worksheets or workbooks when using CF -
which I am not!

Any help much appriciated.

ps - aware can work around it using hidden columns but
this is not really ideal.

Nick