You can use

if isnull(m.field) or empty(m.field)

>I frequently have to do tests to see if a field is blank. Sometimes I can do this with a test for field = "". But. frequently, this test does not return correctly. Even if the field is blank it returns F. So then I have to test against len(alltrim(field)) < 1. This always works.
>
>What am I missing on the first test or should I just stick with len(alltrim)
>
>Dennis