DateDiff function throwing error in Where clause

I have a set of queries that generate dates and want to use DateDiff to
select those records with certain dates are greater than others. The
following clause keeps giving me an incompatible data type error:

WHERE DateDiff('d',[From date],[DatumStvoreni])0

I have the exact expression in the SELECT clause and it show positive and
negative integers just fine, but when I add this test, I get the error.
There are no bad values in the dataset, I've looked, and when I export the
DateDiff column to a temp table and run a query on that, it works fine. Only
when I use the test directly with the DateDiff function does it bomb. I also
tried putting CDate() around the field expressions and it didn't help.

Pete



--
This e-mail address is fake, to keep spammers and their address harvesters
out of my hair. If you want to get in touch personally, I am 'pdanes' and I
use yahoo mail. But please use the newsgroup when possible, so that all may
benefit from the exchange of ideas.