How can I create the HH:MM between a time field and a date/time field?

Oh, I think I understand what you are trying to do...

If you want to know the difference in hours and minutes between 2 separate fields, a date/time and just a time (time of day) field, you might do something like this:

Create a formula duration field and make this the formula (you can reverse the order):

ToTimeOfDay([Date/Time Field])-[Time of Day Field]

Then, set your duration field properties to HH:MM. 

That should do it my friend!