thanks for your answers.
Paul, i wrote the quotes only here not in the formulas.
wapperdude, it's not a mistake. it indeed should be the page property. it should affect all the shapes in the same page.
anyway, the formula i wrote works in a regular shape (not a group). but when i wrote exactly the same formula in the fillforegnd cell of a shape which is a member of a group for some reason it didn't work.
anyone know why?