Query Filtering Based On Form

[Guest]

I have a form with several dropdown fields and I want to filter a query based
on the values chosen on the form. If my user meaves a dropdown blank, then I
want all values for the field shown. Below is an example of an expression I
am trying to use to get the this result. This is just one of the fields in
the query that could be filtered. There are 8 all together.

With this expression, if there is a value entered into the dropdown field,
it works fine, but I get an error if left blank. "This expression is typed
incorrectly or is too complexed to be evaluated..."

How can I let my users either chose a value or leave blank any or all of my
8 dropdown fields and get the desired results?

IIf([Forms]![frmGrowersCriteria]![cboZipCode] Is Null,Is Null Or
[ZIP],[Forms]![frmGrowersCriteria]![cboZipCode])

Thanks in advance,
Clint Herman

 

[Guest]

Isnull is not appropriate to be used there you can use if
len(trim([Forms]![frmGrowersCriteria]![cboZipCode])) = 0 to find out whether
the fields are left blank

Madhuri