Pass a value to the varaible if my selection changes

[#1]

Hi All,

In my file i am doing like this.

I have some selectable fields.

Now i may select some of the fields and create a bookmark  and Xml file with that selectin criteria with same name.(using macro)

Now if i select the same bookmark and select some more fields at this time i want to pass one value to a global variable.But i had no idea how to do it .

Because at this time i don't want to create the bookmark again but the created Xml file will have the new selection criteria.

Can any one help me in this?