How to assign value of item in flexfield in global variable and use it in form personalisation

Hi all,

My goal is to get a value of an item from descriptive flexfield and assign it in a global variable so i could use it again in same form to insert same value in same item in all lines of form so that i make it easy for user to assign it automatic than inserting same values in all lines ..

How can i do it via from personalisation ?