Annoying time problem

[wh00t]

I have the following code to calculate times

Public Function GetTimeCardTotal()

    Dim Db As Database, Rs As Recordset
    Dim totalhours As Long, totalminutes As Long
    Dim days As Long, hours As Long, minutes As Long
    Dim interval As Variant, j As Integer

    Set Db = DBEngine.Workspaces(0).Databases(0)
    Set Rs = Db.OpenRecordset("Hours")
    interval = #12:00:00 AM#
       While Not Rs.EOF
          interval = interval + Rs("hours") - Int(Rs("hours"))
          Rs.MoveNext
       Wend
    totalhours = Int(CSng(interval * 24))
    totalminutes = Int(CSng(interval * 1440))
    minutes = totalminutes Mod 60
   
    GetTimeCardTotal = totalhours & " hours and " & minutes & " minutes"

End Function

this is used when users enter information about people working on a shift to give a total of man hours worked.

the code works fine, but.

the users occasionally return to an entered time and ammend it, unfortunatly I can not figure out a way of automatically reducing the time based on users ammendments.

does anyone have any ideas?