If you have 10/11/2008 15:35:00 in A1, then you can use this in, say,
B1:

=A1+10/(24*60)

as times are stored internally as fractions of a 24-hour day.

Hope this helps.

Pete

On Nov 9, 11:26*pm, Sarah G wrote:
I need to add 10 minutes to a date time field. How should this formulae read
10/11/2008 15:35:00 plus 10 mins would equal 10/11/2008 15:45:00

Thank you