Date Increment() which was suggested is the best option. Only thing you have to remember with that is to use alignment "actual" (it default to start) IF you care about the seconds. If you leave it as default (start), it will remove seconds. You can compare these two formulas
Date Increment( :Col1, "Minute", :Col2)
Date Increment( :Col1, "Minute", :Col2, "actual")
Other option is to add the minutes as seconds to your date (you can use In Minutes() to perform the conversion or multiply by 60)
:Col1 + In Minutes(:Col2)
-Jarmo