excel data label format special number characters
 

I'm trying to create bar graphs containing fractional data labels. The catch
is, I want each bar in the series to have a different denominator value.
Excel allows you to preset the denominator (e.g. - ?/4), but that denominator
affects all members of that series. The question is, is this do-able and if
so what special character(s) allow(s) my task to be performed?