Refresh item data in IRibbon combo box

Hello,
I have a IRibbon combo box control that is dynamically populated with values from a spreadsheet list. The combo box works fine when the spreadsheet is opened and I select the combo box. But if I switch the values based on selection of another combo box, the data doesn't reflect the new list. Only when I close the spreadsheet and open it again.

Is there a way to refresh that data based on selection from another combo box?

I hope I explained it right.

Basically, I want the combo box to behave similar to MS Access combo box when the rowsource is a query. You can requery the data in the combo box with the requery method on the "GetFocus" event .