How to move from control to control using arrow keys

Hi, 

I have made an application in C Windows Api where I have a kind of grid of radio buttons and small edit controls. I want to be able to move between these controls using arrow keys.

I have made the application able to move between controls by using the TAB key. The way I have done this is first to change the message loop like this:

while( GetMessage(&msg, NULL, 0, 0)) {
    if(!IsDialogMessage(Hwnd,&msg)) 	{                                    
       TranslateMessage(&msg);      
       DispatchMessage(&msg);
    }
}

and then using WS_TABSTOP in the create window definitions. However, what I want to do is to move to and from the grid I mentioned by using the TAB key, but when being inside the grid, I will only move from control to control by using the arrow keys. Can anybody help me?

 Thanks in advance.

-Keitel