Pls correct my script for script label creation

Hi,

I want to add the script label name in Masterpages only which was in 'Text thread' options. Is this possible by script?

This is my code

var myTextFrame=app.selection[0];
myTextFrame.label="textpage";
var myNextFrame=myTextFrame.nextTextFrame;
while(myNextFrame !=null)
{    myNextFrame.label="textpage";    myNextFrame=myNextFrame.nextTextFrame;   
}


Instead of first line I want to create this script label "textpage" for master page 'text thread' text frame only

Instead of first line I want to create this script label "textpage" for master page 'text thread' text frame only. How to change my script pls help me?

FYI:

by

hasvi