🚀 go-pugleaf

Good example, so I create a blank document, add 1 text frame which doesn't reach from margin to margin, run the following and it makes the text frame span from margin to margin. That is 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)

' get the margin info
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

' get your text frame bounds
myBounds = DocCDN.GeometricBounds

' subtract Margins from page bounds
myBounds(1) = myNew(1) + MarginB ' left margin have to add
myBounds(3) = myNew(3) - MarginL ' right margin

' size your frame
DocCDN.GeometricBounds = myBounds
End Sub
iolaire