Validating user input of directory creation path

Hi,

Can someone please help. I have a custom page with a DirRequest control. User can also enter the directory path in the text provide and not use browse the directory option.
In such a case I need help on how to validate user input. I need to check if the drive exist. User could enter invalid drive.
I donot want to make the field read only.Kindly help me with this

have a peek at this thread:
http://forums.winamp.com/showthread.php?threadid=302770 - "Validate DirRequest control Path."