Pivot table formula problem

[Russet]

I'm trying calculate the difference between 2 columns in a pivot table. The first column always has a number in it, but the 2nd column is sometimes blank. I want to calculate the difference only if both columns have numbers. The field names are "1st Week" and "2nd Week". I entered this formula =IF('2nd Week'="","",'1st Week'-'2nd Week'), which I thought should work, but I'm getting the 1st Week value in rows where the 2nd Week column is blank. Thanks for any help.

Ken

[romperstomper]

Do you need to distinguish between the second week total being 0 and it being blank?

[Russet]

No, the 2nd Week column has either a positive value or is blank.

[Russet]

The below formula works for me since I'm looking for high positive values.
=IF('1st Week'+'2nd Week'='1st Week',0,'1st Week'-'2nd Week')

[romperstomper]

You should also be able to just test for 0 then:

=IF('2nd Week'=0,"",'1st Week'-'2nd Week')