Parameterized query and ComboBox

Hi,

I'm working with a parameterized FDQuery, connected to an IB DB. I want to assign the parameter (:category) the selected item in the list of items of a ComboBox control. Something like this:

qryCat.ParamByName("category").AsString := ComboBox???

Hope somebody could help me to solve this. Thanks beforehand

JuanCa