Blank as in an empty string, or as a NULL, or as a string filled only with
spaces?
Since you want to use it in a multiplication, I assume you meant NULL:
iif( f5 is null, null, f5 * j5 )
( or simply, Nz( f5 * j5, "" ) )
where I also assume j5 is a decimal value, such as 0.05 when the meaning
can be read as 5% once formatted.
Note that if f5 is null, the formula return a null, not a zero length
string. If you need it, inside another computation, you may prefer to use a
zero:
iif( f5 is null, 0, f5 * j5 )
or simply just:
Nz( f5 * j5, 0)
since, if f5 is null, f5 * j5 will produce a null, all by itself, and Nz
will replace it with a zero, or with an empty string as in the first
supplied alternative.
Vanderghast, Access MVP
