Combo Box Query

[aids2]

I have a form that contains 3 combo boxes that are used as the basis for a query.
The problem I have is 1 or more of the combo boxes can contain a null entry.
How do I get the query to search for the 3 parameters even if 1 is empty?
I have tried using combinations of the And/Or criteria and none of them seem to work. I have tried concantenating the fields together and then using my combo criteria to search the new field.
Any guidance on this problem would be greatly appreciated.

 

[jioek]

in the query use like "*" & [mycombobox]
or try nz(mycombobox) 'null to 0 funtion'
that will return all