null value shows all records in subform

[Ron Fontanillas]

Hi All,

I'm new here and also new with Access 2007.
I have a Form named "Copy_of_Qry" and a subform named "qrysubform". the subform is based on a query with column headers Year, Month, PIC, etc.

I've made three combo boxes, all which are supposed to filter the query (subform), one for the Year(cmbYR), then month(cmbMonth), then PIC(cmbPIC). I just used the parent/child linking method. What I would like is that when I select the PIC and the year, and when the month is null/empty, records for all month would be shown on the subform.

can anyone please assist? thanks in advance!