Can't Set workbook to ActiveWorkbook

Hi, for some reason I'm not able to set a workbook to ActiveWorkbook, it appears as "activeworkbook" thus the macro does not function.

Dim Macrobook As Workbook
    Dim wb2 As Workbook
    Dim rngCell As Range
    Dim macrosheet As Worksheet
    Dim ws2 As Worksheet
    
    Application.ScreenUpdating = False
    Set Macrobook = activeworkbook
    Set macrosheet = Macrobook.ActiveSheet