conditional formatting based on PART of a cell value

I have a series of cells that contain fractions such as 5/24 or 7/18. I need to be able to turn those cells into "progress bars" with conditional formatting, with the low number being 0 and the high number being 24, or 18, etc. The 5 or 7 is obtained with the formula =COUNTIF(A1:A25,"Y"), but the second number (24 or 18, etc) is manually written in. So the actual formula in the cells that display "5/24" is actually =COUNTIF(A1:A25,"Y")&"/24". Is there any way to use the denominator ONLY when doing conditional formatting? Or if this isn't possible, is there a way to do it in VBA?