App that renames all files in directory

I've got a list of files that need renaming. The list looks like this... [login to view URL] [login to view URL] [login to view URL] [login to view URL] [login to view URL] [login to view URL] ... etc. Any file that ends in "a" should be renamed to TWICE the coefficient. In other words, [login to view URL] should be called 44.gif. (22 x 2 = 44) Any file that ends in "b" should be renamed to TWICE the coefficient PLUS 1. In other words, [login to view URL] should be called [login to view URL] (22 x 2 + 1 = 45) App should ask me for the directory where the files are contained (include navigation/file-finder thing so I don't have to type in the path). Also, provide some sort of progress bar or something and a "Finished!" dialog box. It'd be nice also to do some basic error checking to verify that the directory contains ONLY numbered files followed by A or B. [* NOTE - Although I used .gif as the example, it's possible that the files may have different extensions, so we're working with just filenames - leaving extensions as they are.] How easy can it get? I'm sort of in a hurry on this, so the faster you can get this done, the better. Any questions, let me know. Thanks for bidding! ## Deliverables 1) Complete and fully-functional working program(s) in executable form as well as complete source code of all work done. 2) Installation package that will install the software (in ready-to-run condition) on the platform(s) specified in this bid request. 3) Complete ownership and distribution copyrights to all work purchased. ## Platform Windows