I have tried a couple different formulas however I can't get the output\result to be hh:mm:ss (example: 00:45:06)
This is the most currently formula I tried. DateTimeDiff([LogoutTime],[LoginTime],'%H:%M:%S'). I get an error that this will return a number and I have it set to Time. I changed the data type to string however then I get no results, even through the error is gone (just null in the field).
This is my excel from excel, the Different column is what I would like to see.
O.k. - datetimediff returns only one thing so it has to be seconds/minutes/hours etc... you can parse that as it is into a number or you can keep it as a time and then do a datetimeformat([whatever value you got above],"%H:%M:%S") to get it into a H:M:S: format.
datetimeadd adds a unit of time to an amount of time the result is date/time.
datetimediff compares two date/times and comes back with the difference in a unit of time as expresses as the amount of units.
datetimeparse allows you to bring into date time a string based upon various formatting options
datetimeformat returns elemnts of a date time in a string format.
So the difference of two times - which you are looking for - is a number either in minutes/seconds/etc. you can then manipulate that into component parts and back into a time... using datetimeparse - or datetimeadd as shown by @Emil_Kos's superior workflow