You can have a defined cell format that is dependent on a variable; however,
if I understood your request correctly, you can do what you are asking for
with some VBA code though. Give this a try...

Right click the tab at the bottom of your worksheet and then click View Code
from the popup menu that appears and then copy/paste the following code into
the code window that opened up...

Private Sub Worksheet_Change(ByVal Target As Range)
Const FormulaCell As String = "J8"
If Target.Address = "$I$8" Then
Range(FormulaCell).NumberFormat = "# " & String(Len(Target.Value), _
"?") & "/" & Target.Value
End If
End Sub

Next, change the example J8 cell reference I used in my code above to the
actual address of the cell that contains the formula you posted. Okay, now
go back to the worksheet and enter a value in cell I8... you need to do this
one time in order for the first format to be assigned (everything will be
automatic thereafter), so you can just type the number that is already in
there over again if you want. Now, whenever you change the value in I8, the
format in the cell you changed my example J8 reference to will change to a
Fraction format with the denominator being the value in I8.

--
Rick (MVP - Excel)


"fractionwoes" wrote in message
...
I am trying to set up a depreciation schedule and I want the denominator of
fraction to stay a constant - do not round or reduce. For instance, if
the
months, cell I8, (the denominator) is 72, then the formula
=IF(F13="","",((F$5-F12)/I$8)) would give the answer of 2/72, 3/72, 4/72,
etc. But the denominator won't always be 72, it might be 150, etc. I
have
tried to format the cell to # ???/???, but Excel keeps reducing the
fraction.