If you use optionbuttons from the Forms toolbar, put a groupbox (also on that
same toolbar) around the optionbuttons.
And then rightclick on an optionbutton on that group, choose Format
Control|control tab. Then assign the linked cell.
If you use optionbuttons from the control toolbox toolbar, rightclick on each
of the members of the group, choose properties, and give that group a unique
groupname.
You can assign the Linkedcell on that properties window.