Change Numeric Constants In Column To Zeros

I have the following code

Call LastCell_Example(LastCell)
lastrow = Cells(Rows.Count, "B").End(xlUp).row
Set Datarange = ActiveSheet.Range("B1:" & LastCell)
' Set to 0 all cells that contain constants, but ONLY those that are numeric
Datarange.SpecialCells(xlCellTypeConstants, xlNumbers) = 0

lastcell_example contains

Dim rng As Range

' Use all cells on the sheet
Set rng = Sheets("Courtage").Cells

' Find the last cell
LastCell = Last(3, rng)

' Select from A1 till the last cell in Rng
With rng.Parent
.Select
.Range("A1", LastCell).Select
End With

When I run the code above, I don't understand the fact that the first rows in the sheet AFTER "Courtage" are also being changed to zero.

Obviously, I'm not limiting my datarange correctly, but could someone explain what I need to do to limit the changed data to ONLY the current sheet.