"Filename already exists" error and handling

I have many instances where I have more than one copy of a song. As a DJ this is especially true but even in the case of a track being on a studio album and then a compilation/greatest hits.
I use a simple filenaming script and when using the convert function to name my files within Mp3Tag, the program will display an error if it attempts to name a file to a string that already exists in the same directory. Most programs, including Windows Explorer in general have a built in function to add text to the end of the filename, such as "(1)" to signify the name is a duplicate. Mp3Tag doesn't seem to do this automatically and I can't figure out how to write my script to make this happen. Suggestions?

In summary here's an example.

Title: ABC
Artist: Jackson 5
Album: ABC

Title: ABC
Artist: Jackson 5
Album: Motown Greatest Hits

desired filename for track 1:
Jackson 5 - ABC (1).mp3

desired filename for track 2:
Jackson 5 - ABC (2).mp3

Thank you for your time,

See /t/9637/1