Option Explicit

Private Sub Document_ContentControlOnEnter(ByVal ContentControl As ContentControl)
Dim oCCS As ContentControl
Dim oCCE As ContentControl
Dim oCCD As ContentControl
    Set oCCS = ActiveDocument.SelectContentControlsByTitle("Start").Item(1)
    Set oCCE = ActiveDocument.SelectContentControlsByTitle("End").Item(1)
    Set oCCD = ActiveDocument.SelectContentControlsByTitle("Days").Item(1)
    Select Case ContentControl.Title
        Case "Start"
            If oCCD.ShowingPlaceholderText = False And oCCE.ShowingPlaceholderText = False Then
                MsgBox "Make your change then click outside the field to update the day count."
            End If
        Case "End"
            If oCCE.ShowingPlaceholderText = False And oCCE.ShowingPlaceholderText = False Then
                MsgBox "Make your change then click outside the field to update the day count."
            End If
            If oCCS.ShowingPlaceholderText = True Then
                MsgBox "Complete the start date field before clicking here"
                GoTo lbl_Exit
            End If
        Case "Days"
            If oCCS.ShowingPlaceholderText = True Or oCCE.ShowingPlaceholderText = True Then
                MsgBox "Complete both date fields before clicking here"
                GoTo lbl_Exit
            Else
                oCCD.Range.Text = CStr(fcnCalcDays(oCCS.Range, oCCE.Range))
            End If
        Case Else
    End Select
lbl_Exit:
    Exit Sub
End Sub

Private Sub Document_ContentControlOnExit(ByVal ContentControl As ContentControl, Cancel As Boolean)
Dim oCCS As ContentControl
Dim oCCE As ContentControl
Dim oCCD As ContentControl
    Set oCCS = ActiveDocument.SelectContentControlsByTitle("Start").Item(1)
    Set oCCE = ActiveDocument.SelectContentControlsByTitle("End").Item(1)
    Set oCCD = ActiveDocument.SelectContentControlsByTitle("Days").Item(1)
    Select Case ContentControl.Title
        Case "Start"
            If oCCD.ShowingPlaceholderText = False And oCCE.ShowingPlaceholderText = False Then
                oCCD.Range.Text = CStr(fcnCalcDays(oCCS.Range, oCCE.Range))
            End If
            If Val(oCCE.Range.Text) < Val(oCCS.Range.Text) And _
               oCCE.ShowingPlaceholderText = False Then
                MsgBox "The start date is later than the end date?"
                oCCE.Range.Text = ""
                oCCD.Range.Text = ""
                GoTo lbl_Exit
            End If

        Case "End"
            If Val(oCCE.Range.Text) < Val(oCCS.Range.Text) And _
               oCCS.ShowingPlaceholderText = False Then
                MsgBox "The start date is later than the end date?"
                oCCE.Range.Text = ""
                oCCD.Range.Text = ""
                GoTo lbl_Exit
            End If
            If oCCD.ShowingPlaceholderText = False And oCCS.ShowingPlaceholderText = False Then
                oCCD.Range.Text = CStr(fcnCalcDays(oCCS.Range, oCCE.Range))
            End If
        Case Else
    End Select
lbl_Exit:
    Set oCCS = Nothing
    Set oCCE = Nothing
    Set oCCD = Nothing
    Exit Sub
End Sub

Function fcnCalcDays(Date1 As Range, Date2 As Range) As Long
Dim lngDays As Long
Dim lngIndex As Long
Dim dTest As Date
    lngDays = 0
    dTest = Date1.Text
    For lngIndex = 1 To DateDiff("d", Date1.Text, Date2.Text)
        If Weekday(dTest, vbUseSystemDayOfWeek) <> 6 Then
            lngDays = lngDays + 1
        End If
        dTest = DateAdd("d", 1, dTest)
    Next
    fcnCalcDays = lngDays
lbl_Exit:
    Set oCCS = Nothing
    Set oCCE = Nothing
    Set oCCD = Nothing
    Exit Function
End Function

Sub ClearDateFields()
Dim oCCS As ContentControl
Dim oCCE As ContentControl
Dim oCCD As ContentControl
    Set oCCS = ActiveDocument.SelectContentControlsByTitle("Start").Item(1)
    Set oCCE = ActiveDocument.SelectContentControlsByTitle("End").Item(1)
    Set oCCD = ActiveDocument.SelectContentControlsByTitle("Days").Item(1)
    oCCD.Range.Text = ""
    oCCE.Range.Text = ""
    oCCS.Range.Text = ""
lbl_Exit:
    Set oCCS = Nothing
    Set oCCE = Nothing
    Set oCCD = Nothing
    Exit Sub
End Sub