Work hours between 2 dates(not working -VBA)

[Bob Phillips]

This code does it.

Const WORKING_DAY_END As String = "18:00"
    Const FORMULA_WORKING_TIME As String = _
    "=(INT(E2-D2)*(""" & WORKING_DAY_END & """-""" & WORKING_DAY_START & """)" & _
    "+MEDIAN(MOD(E2,1),""" & WORKING_DAY_END & """,""" & WORKING_DAY_START & """)" & _
    "-MEDIAN(MOD(D2,1),""" & WORKING_DAY_END & """,""" & WORKING_DAY_START & """))"
    Dim lastrow As Long
    With ActiveSheet
         lastrow = .Cells(.Rows.Count, "G").End(xlUp).Row
         With Range("G2").Resize(lastrow - 1)
              .Formula = FORMULA_WORKING_TIME
              .Value = .Value
              .NumberFormat = "[h]:mm"
        End With
    End With

I have used all the constants so as to make it easy to amend if the start/end day times change. I have also output the answer as hh:mm as this makes more sense (to me) than decimals.