Document.CompatibilityMode (Word)

Returns a Long that specifies the compatibility mode that Word uses when opening the document.

When you open a document in Word that was created in a previous version of Word, Compatibility Mode is turned on. Compatibility Mode ensures that no new or enhanced features in Word are available while working with a document, so that people who edit the document using previous versions of Word will have full editing capabilities.

Sub InsertCheckbox()
       
    If (Application.Version = ActiveDocument.CompatibilityMode) Then
          Selection.Range.ContentControls.Add (wdContentControlCheckBox)
    End If    
End Sub