🚀 go-pugleaf

Tony, 

The "Master Text Frame" checkbox only exists in the "New Document" dialog box. It simply puts a text frame on the pages on the master. You can accomplish the same thing from scripting by simply creating a text frame on the master spread. 

To access a text frame that appears on a master, you first need to detach them from the master by overriding them, then you can get/set the frames' previous/next properties. 

Here is an example: 
Set ID = CreateObject("InDesign.Application")
Set myDoc = ID.Documents.Item(1)
Set myMaster = myDoc.MasterSpreads.Item(1)
' Add the first page
Set newPage1 = myDoc.Pages.Add
' Set the first page's applied master
Set newPage1.AppliedMaster = myMaster
' Override the text frame on page 1
Set newFrame1 = newPage1.MasterPageItems.Item(1)
' Add the second page
Set newPage2 = myDoc.Pages.Add
' Set the second page's applied master
Set newPage2.AppliedMaster = myMaster
' Override the text frame on page 2
Set newFrame2 = newPage2.MasterPageItems.Item(1)
' Connect both frames together
Set newFrame1.NextTextFrame = newFrame2 

-peter