Access 2000 – adding time

I have a form which calculates number of minutes form other fields in the DB. I want to add this number to another field “start time” which is formatted as time. e.g. 07:00 [formatted as time] + 15 minutes [formatted as number]. Is there any wayof doing this, or can I convert the 15 mins to time somehow and add it to the start time? Can you help, I’m running out of time!