Calculating the Distance between the Top of the Window and Row 1

My Excel Toolbox includes the following function to determine the screen coordinates of the top-left corner of the first cell in a range:
Public Function Range_ScreenXY(rTarget As Range, _
    Optional sUnits As String = "pixels") As Long()
This function returns a base-0 Long array XY() with 3 elements:
XY(0) = rTarget's original ActiveWindow.Zoom before adjustment (see below)
XY(1) = screen X-coordinate for rTarget.Left
XY(2) = screen Y-coordinate for rTarget.Top
Optional sUnits specifies the units of returned screen coordinates; only the first two characters apply and alphabetic case is ignored. The following sUnits are recognized: "pixels" (default) or "pi" or "px", "points" or "po" or "pt", "twips" or "tw". Pixels are screen pixels, not Windows' pixels, which might differ; see the DisplayScreenMetrics macro.
If necessary, ActiveWindow.Zoom will be adjusted to the nearest multiple of 5 (like 75, 80, 85...); otherwise, results are close but randomly unreliable. Results are best if Zoom > 65. If necessary, ActiveWindow will be scrolled southeast (SE) to make room for a dialog box at X-Y. This function accommodates Split with or without FreezePanes (unlike Pearson's, which might not handle Zoom either).
Note: UserForm position is based on the top-left corner of the screen (not the program window) in points (not pixels).
Note: Microsoft documentation is incorrect for PointsToScreenPixelsX/Y methods, which are reliable only when their argument is zero; see http://microsoft.wmlcloud.com/forums/t/120412.aspx.
Here is an example macro that uses Range_ScreenXY to position a UserForm:

Sub PositionUF()
    Dim UF As UserForm1, rSele As Range, sAddr As String
    Dim XY() As Long, nZoom As Long
    Const Msg = "Using the mouse, select a cell to position the UserForm." _
        & vbNewLine & "Click OK to continue or Cancel to quit."
    Const Title = "PositionUF"
    Const AdjustX = 6 'determine empirically for your configuration
    If TypeName(ActiveSheet) <> "Worksheet" Then Exit Sub
    nZoom = ActiveWindow.Zoom
    Set UF = New UserForm1
    UF.StartupPosition = 0
    Set rSele = Selection
    Do While True
        sAddr = rSele.Cells(1).Address
        Set rSele = Nothing
        On Error Resume Next
            Set rSele = Application.InputBox(Msg, Title, sAddr, Type:=8)
        On Error GoTo 0
        If rSele Is Nothing Then Exit Do 'user clicked Cancel
        XY = Range_ScreenXY(rSele, "points")
        UF.Left = XY(1) - AdjustX
        UF.Top = XY(2)
        UF.Show vbModeless
    Loop
    Unload UF
    Set UF = Nothing
    ActiveWindow.Zoom = nZoom
End Sub

See https://sites.google.com/view/MyExcelToolbox