Excel Problem - Decimals for years.months

[erolb]

Afternoon

How do I format cells in Excel 2003 or 2007 so that I can put years and months as decimals and have the number to the right of the decimal point roll up when it gets to 12?

i.e

9.8 would be 9 years, eight months. When it reaches 9.12 it rolls up up to 10.0

Wife's a teacher and she's recording reading ages and has to do calculations such as add on 1 year 3 months.

Thanks in advance, boffins.

[lestag]

maybe this can help? http://www.excelbanter.com/showthread.php?t=179812

[erolb]

Yeah, I looked at that. It simply shows the difference between two dates as a decimal. Basically what I'm trying to do is set the roll-over over a decimal from 10 to 12.

Thanks for responding though.