- select the used area and make sure A1 is the active cell
- in Format>Conditional Formatting enter Formula is =MOD(ROW(A1),10)=0
- select format and it will be applied to every 10th row
HTH
Anders Silven
P.S. Just before sending this reply I see Gord Dibbens message that you have
posted the same question in another group. Please don't do that, you are wasting
peoples time.