Excel 2007 : Remapping END key to a colon

I have a worksheet that requires data entry on about 5 sheets. One of the sheets is concerned with entering times in the format of, eg

11:10:00

for 11.10am.

In order to make entering these figures easier and to avoid having to use both hands (one for ctrl, the other for : ), I set up auto correct to change . to : (decimal point to colon)

This is fine, but it means that I have to go the Auto Correct Options to set up or cancel this whenever I enter or leave the time sheet, as I need an ordinary decimal point for the other sheets.

Is it possible to remap a key, say the END key which I don't use, so that it produces a colon instead? I could then stick a piece of paper with a colon on it over the END key. This would make entering data much easier.

Thanks if anyone can help.

btw, I'm using Windows 7