HELP!! Conditional format - if cell is greater or less than the sum of the range of cells

Hi,

I've looked around for an answer to this without success.

I have a spreadsheet where I need the "18" change and be highlighted as green if the sum of the next 4 columns with a check is greater than 18.Stay in yellow if equal to the sum, and red if under.

Tried to use =SUM(Col1:Col4), and =SUM(S642,T642,U642,V642) but it is not working..