Filter a List box using a Combo Box (1 Viewer)

Hi all-

I have a list box and a combo box on a form based on a query. The list box is a multi-select, with column values of Client, ClientEmail, and Medical.

Medical is a simple yes/no field, and it is what I want the combo box to help sort by. I have a Where clause in the query: WHERE (Medical=[forms]![frmOne]![cmbbx]), and the only values in the combo box are Yes and No (1 column). I also have the combo box set to run a requery macro after updating. I've also tried to change the macro to VBA:

When I pick a string from the combo box, the list box just goes blank, rather than updating to clients who either do or don't have Medical, and I can't understand why.

If I forgot to put in any information you need, let me know and I'll respond ASAP.

Thanks for any help in advance

You need the After Update event of the ComboBox where you set the criteria as,