It depends on where the bat-file itself resides on what program you try to start etc. For instance, to get the drive letter of the batch file path you could use SET DRIVE=%~d0 in your batch file. On the command line (cmd.exe) have a look at "help for", this might help you with this. Or have a look at http://www.robvanderwoude.com/batchhowto.php
I know it will take some time to master this... I'm sorry I can't come up with a ready-to-use solution.