If they are part of an Option Group, you could return the value of the Option Group(it changes every time you select an option). If it is not you can loop through the form looking for the option button's value.
Private sub CheckOpBut()
Dim ctl as control
dim i as integer
for each ctl in me.controls
if typeof ctl is OptionButton then
if ctl.value = True
else
end if
end if
next
This routine needs to be fleshed out, but it should work.
Hope that helps.