Access custom date/time format and input mask error - date

Question

I have a database that I need to store a bunch of times and do calculations based on the times, however, the times can be over different days so using just a time format wont calculate the correct difference between the two. For ease of use I wanted to limit how much of the date they have to input because there is a bunch of times and I dont want to have to type the full date each time. I created the following custom format: 16-Jan 15:00 (d-mmm h:nn)
I also created a custom input mask to go with this: 90-LLL\ 90:00
My form fields have the same format and input masks to match. The initial input of the field works right, the issue comes when I try to edit a field and change one digit. It pops up with the error that it doesnt match the input mask, even though it does. In order to change the field I have to delete everything, remove focus from the textbox and then click back in. Is there anyway to fix that? Or is there another option to calculate the difference between the times without having to use the date when it could be over 24hrs long (not longer than 48 though)

Answer 1

Yes, you can have a checkbox, NextDay, to mark if the end time is of the following day.
Then your timespan will be:
Dim Timespan As Date
Timespan = CDate([EndTime] - [StartTime] + Abs([NextDay]))
To input the time, you can use the method here: Entering 24-hour time
To format and display your timespan, also for values above 24 hours, use a function like this:
Public Function FormatHourMinute( _
ByVal datTime As Date, _
Optional ByVal strSeparator As String = ":") _
As String
' Returns count of days, hours and minutes of datTime
' converted to hours and minutes as a formatted string
' with an optional choice of time separator.
'
' Example:
' datTime: #10:03# + #20:01#
' returns: 30:04
'
' 2005-02-05. Cactus Data ApS, CPH.
Dim strHour As String
Dim strMinute As String
Dim strHourMinute As String
strHour = CStr(Fix(datTime) * 24 + Hour(datTime))
' Add leading zero to minute count when needed.
strMinute = Right("0" & CStr(Minute(datTime)), 2)
strHourMinute = strHour & strSeparator & strMinute
FormatHourMinute = strHourMinute
End Function