How to update "Text" into by ACL script?

Could you please help me to get to know about ACL Command or function to copy the text of an element and paste it in another element/attribute...

1st time I construct the DITA map

<map><title>Hello</title>

<topichead navtitle="Hello">

some reason the "title" is updated or translated...

after update the map is like

<map><title>How are you</title>

<topichead navtilte="Hello">

I want to update topichead/@navtitle by a ACL script so <topichead navtitle="How are you">.