I am having a problem coming up with a formula for what I want.

I have cells E15, F15, G15 and H15. All of them have checkboxes and the
boxes are linked to each cell.

What I want is over in cell K15 I want a message to appear if more than one
box is checked in that row only. Something simple in bold red like "Only
Check 1 Box"

I get as far as =if(E15)=TRUE..................then I am lost.

Thanks in advance for any help