Get List Count in external application

Hi,
I'm trying to get the count in the list/grid from an external application(IP messenger) from my application using windows API in C#. I'm able to get the handle of the list. but when i try to get the count in the list(here it is a grid) its giving me a wrong value(always 8). I used the following code to get the count.

int count = SendMessage(listHandle, Convert.ToInt32("0x1000", 16) + 40, Convert.ToInt32("00000000", 16), Convert.ToInt32("00000000", 16)) - 1;

where listHandle is the handle of the grid. This is a C# code.
Can someone help me out in this. I dont know where i've made the mistake. Or is there any other way to get the count from an external application. Pleas ehelp me out in this.

Thanks in advance
Vinoth