Another way around all this is to change the time separator in the Regional settings to a period "." It is not there as a selectable option but just type it in and Apply.
This however WILL cause you much grief if you leave it that way
so I would suggest changing it, running your calculations and then CHANGE IT BACK. There are other programmable ways around it by using the instr function to search for the "." and then the left and mid functions to split up the hours and minutes This would only be necessary if the input does not have leading zeroes ie 5.45 Vs 05.45, other wise left(value,2) = the hour and right(value,2) = the minute.
If the file is small enough email me a sample and I will have a look.