Hi Mallet,
Good work! However I think you might want to take a look at the one used by Genpact (formerly GE Capital Int'l Serrvices). For reasons of copyright, I will not upload it here, but you can always ask someone from Genpact to pass it on to you for a look...it is used very widely there..has been validated by use over last 7 years...is comprehensive and very well designed...though you might have to change a few assumptions for use elsewhere.
Just for the the record - Genpact's employee attrition is less than industry average by 1/3rd...of course, this tracker plays only a small part in the overall effort at conatinment