unable to click on the treeview child item programatically Win32/C/C++

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C++

C

Win32

My question is simple - "In application with lots of data, I am unable to click on the treeview child item". Kindly read detail explanation:

I am creating a function to simulate a treeview control in another process. So far I have succeded in
1.Getting handle of Tree view control handle of another process using Hooking technique.
2.Getting handle of root and other item of treeview.

For Eg: Now I need to click on an child2 (Parent1->child1->child2).I checked in small sample application it worked well.Next I started to test using real application , in that application when parent1 is clicked only "Dummy items" appear. I know for performance, when treeview control is loaded for the first time Parent1 will contain "Dummyitems". After clicking/Expanding on parent1 it will fetch the data from DB and display its contents. But for me when I click the parent item programatically it only displays "dummyitems" for the first time,So I am unable to click on other items. Kindly help.