Radgrid get_masterTableView() is null in radwindow

[systems]

Hello,

We have a Rad grid and a hyperlink in a rad window

Here on hyperlink click we are trying to bind the rad grid from client side by calling Web Method via $.Ajax() function, however 

the rad grid  - get_masterTableView() finds null.

So, could someone please advise is there any workaround/better way to bind the rad grid as per the above case?

Thanks in advance.