Can anyone help?

I have two columns, one containing previous time (eg 3.10.04, ie 3 minutes, 10 seconds and 04 milliseconds) and 2nd column containing new time (eg 3.12.89).
I need a formula to give me the difference between the 2 times (result may be positive or negative time). I formulated the columns to be "time" but result in #VALUE! error.