Using Excel 2003;

I am trying to format a range of cells to accept hardware dimensions so I
can sort them by product code, diameter, pitch, and length. Since I can only
sort 3 columns, it would be helpful to combine pitch and diameter in a custom
number format.
Ideally I want to be able to enter diameter and pitch in the same cell as
follows:
"(diameter in whole numbers or fractions)-(pitch in whole numbers)"

For example, here are some common sizes:
10-24
10-32
1/4-20
5/16-18

I know how to get to the custom number format, but I don't understand how to
use the number codes to create the custom number format I need.