How to not fire the datagridview checkbox check base on some value

I have a datagridview that has pairs of lines on for office one for Loc with each having a row key example 1 Off some val 1 loc some val where each value above is in a seperat col of the DGV. there is also a check box on each row. i have written code to not allow both lines with the key value to be checked and display an error to the user. here is the scenario user clicks on line 1 OFF it clicks the check box is checked it checks to see if its matching pair is already checked if not then the box is checked. the user clicks the matching pair 1 loc it checks it matching pair finds it is checked i pop a message then uncheck the check boxs for 1 loc.

I would like to stop the checking from ever taking place just check if its pair is checked don't even fire the cellchangeevent.