|You described almost to a T the description of what it is you need. |
What you want to do is use a variable in place of the hardcoded path.
In your case, you'll have one of tow choices.
If you want just the current username to be a part of your path you can use:
C:\Documents and Settings\%Username%
If you want to make sure you're full proof against any anomalies in system drive (as well as the added benefit of typing less ;) ) you can use the %userprofile% variable, which would be equal to the full path (i.e C:\Documents and Settings\JoeUser ) independent of what their system drive letter is.
You can find a full list of variable available here: