Filtering ListGrid tools from element of Ajax-Subform

For loading spesific form using value from popup select box, i'm using ajax subform.

with configuring in ajax subform :

• Cheked 'Reload Sub Form when Parent Field value change' config
• 'Parent Field Id to keep Subform Id' = (Popup Select Box Id while 'ID Field' in this popup will refer to id/key in subform)
• 'Subform Field Id to keep Parent id' = id/key in subform

limititation from this method, it's loaded page with ajax request and imposibble to get any element value from parent form or other subform

except accessed inside the same ajax-subform.

On the same ajax subform, i will insert ListGrid tools.

whenever i need to fill up this ListGrid, when selecting data, that data automatically filtered by any element on that loaded form.

but i'm affraid it's hard to implements this method.

Possible solutions is,

ListGrid will auto populate with some criteria from any element in that loaded form

GridList will have Beanshell Load binder and will make some query base on that criteria.

the question is,  How can i achieve this solution.

maybe if every tools which need other form/datalist lookup references (e.g popup select box, Selecting data from ListGrid) can using request parameter for filter whatever will show up in lookup popup form,

it will much better and will make life of joget developer more easier