Capture Text from external app datagrid

I am having trouble finding the correct message for hooking to retrieve text from external app which uses windowsforms10.window.8.app.0.378734a class window to display data in a grid. I want to capture the data when data of any cell changes. I have tried Spy++ for messages but it seems it send only WM_Paint and WM_ERASEBKGROUND messages. I tried to hook WM_PAINT and i am able to get WM_PAINT message in my program but lParam and wParam both contains 0 so i am not getting the idea from where i can get the data. I injected a DLL to capture all the msg from that app but still not able to find out the method. Is there any way to capture CellValueChanged event of this data grid. Please help otherwise this problem will make me crazy.

Without knowing the app, I'd guess that they are blocking messages.

Yes may be messages are blocked by that application. But i know there is one program ( Say B) which is able to capture data from this grid. Grid used in that external program (Say A) is component1 flex grid with C1.Win.C1FlexGrid.dll. I have studied and found that the program (B) which reads data from external app (A) grid injects two DLL files in the external process. I can post these DLLs if it can help.

I have checked with Spy that no subclassing is done by program (B) as wndProc address of all the windows/grid controls in program (A) remains same even after injecting the DLLs by Program (B). Other intresting thins is that once these DLLs are injected and data starts coming from Program (A) and then even if i unmap/unload these two DLLs then also data keeps coming. Does it means that some code has been written/modified in the loaded C1.Win.C1FlexGrid.dll memory so that data keeps coming even after unmapping these two injected DLLs.

Total situation is so confusing that i am not able to understand how to go about.

Please help me ...

Thanks