Can I do math on date and time values – specifically add a number of minutes to a time value?

I have an agenda planner spreadsheet in Excel which stores session start times as (e.g.) 3:00 PM and calculates the start time of the next session by adding to it another field which holds an integer number of minutes. In Excel I do this using the formula =B18+TIME(0,A18,0) where B18 is the current session start time and A18 is the duration of the session in minutes.

Numbers doesn't like that formula and I can't work out whether there is an equivalent way of doing this in Numbers.

Any suggestions?

Many thanks!