part of form closes before another part and causes error

[Ken Ivins]

I have a form (frmCustomer) with a combo box cbxcuCounty which is a drop
down list of Counties. Else where I another combo box (cbxcuPlans) (on a
tab) of pricing plans based on the county of the customer. To achieve this
I created a query of all the plans that looks to the cbxcuCounty field then
returns only the plans and pricing for that county.

I thought this was great except that when I exit the form I get a Enter
Parameter Value asking for the value of the cbxcuCounty. I assume this means
part of the form or table is closing before other parts and it is trying to
query a field that is closed.

What can I do to avoid this or is there a better way to make this happen.

Thanks for your help.