Using javascript in Acrobat XI. For some reason, I keep getting the following error:

invalid assignment left-hand side at 9: line 10

My code is pretty simple and looks spot on AFAICT. Please review and tell me I'm not crazy. (Or tell me I am, but you have a solution :))

function jsNetworkAccount()

{



    // Get a reference to each check box

    var f1 = getField(cbNetworkNotNeeded);

    var f2 = getField(cbNetwork);

    var f3 = getField(cbEmailAccount);



    if (event.target === f1 && event.value = On) {



           f2.value = Off;

           f3.value = Off;

           return;

    }



    if (event.target === f2 || event.target === f3 && event.value = On) {



           f1.value = Off

           return;



    }    

}