Yes, it will make it a little harder, but it can be done.
Try this: (UNTESTED)
you will need the code from
http://www.accessmvp.com/djsteele/Diff2Dates.html
(put the "Diff2Dates" function in a standard module)
Code:
Private Sub cmdDoCalc_Click()
Dim dtStart As Date
Dim dteEnd As Date
' combine the dates/times
dtStart = DateValue(Me.StartDate) + TimeValue(Me.StartTime)
dteEnd = DateValue(Me.EndDate) + TimeValue(Me.EndTime)
' the function Diff2Dates is from http://www.accessmvp.com/djsteele/Diff2Dates.html
Me.Elapsed = Diff2Dates("dhns", dtStart, dteEnd)
End Sub