Excel Custom Ribbon toggle button dependency

I'm trying to put together a custom menu, and I want 2 of the toggleButtons:"chkToggle1" and "chkToggle2" to exclude each other, meaning that when 1 is checked the other is not and vice versa.

            <checkBox id="chkToggle1" getLabel="onGetLabel" getScreentip="onGetScreentip"   getSupertip="onGetSupertip" getPressed="GetPressed" onAction="tgl_ClickAddin" />
            <checkBox id="chkToggle2" getLabel="onGetLabel" getScreentip="onGetScreentip"   getSupertip="onGetSupertip" getPressed="GetPressed" onAction="tgl_ClickAddin" />

Can you guys give any ideas on how I can do that? Ideally there should be a way to get the pressed value from another control by control.id without using global variables, but Google is not helping me, maybe you can.