🚀 go-pugleaf

Is this what you mean? (I don't really understand what you want.)
Sub testing()
Set myInDesign = CreateObject("InDesign.Application.2.0")
Set myDocument = myInDesign.ActiveDocument

' here I just pick a page to measure = 1, you probably want to use your current page
Set my_page_items = myDocument.Pages.Item(1).AllPageItems
' here I set DocCDN to page item = 1, you want to use your object to change
Set DocCDN = my_page_items.Item(1)

MarginB = myDocument.Pages.Item(1).MarginPreferences.MarginBottom
MarginL = myDocument.Pages.Item(1).MarginPreferences.MarginLeft
' get bounds of page = 1
myNew = myDocument.Pages.Item(1).bounds
' subtract Margins from page bounds
myBounds(1) = myNew(1) - MarginB
myBounds(3) = myNew(3) - MarginL
DocCDN.geometricbounds = myBounds
End Sub