smcadman,
You should learn to abuse Microsoft Excel a little.
1. Create a design table.
2. Place your length in a cell. This is the best way to manage multiple lengths anyway. Assume that your length is cell c5
3. Create a cell that controls configuration specific data. For example, the header $PRP@SPEC will create a configuration specific entry called SPEC.
4. Your entry for the relevant cell is "LENGTH: "&c5. This concatenates the contents of cell c5 onto the end of your text.
This is really powerful, especially if you are trying to build a database of standard parts.
JHG