picture control to use a a 2D graph

[rafraf]

Hi,
I am trying to build a 2d graphic in my program. I started using the picture control, using it as rectangle.
What I am not being able to do is to get the size of this window (picture frame) using API.
To update the frame I paint a white rectangle inside the picture control and them I draw some lines. but to paint this white rectangle I need to know the size of the picture frame.

here it goes a peace of my code where I update the window cleanning it before. I have never used GDI before and now I am a bit confuded with everyting I am seing of new...I am trying to stand always on API...If anyone can help I thanks...

bool graph2D::update()
{
int i;
HDC hdc = NULL;
if (hframe==0) return FALSE;
hdc = GetWindowDC(hframe);

SelectObject(hdc , GetStockObject(WHITE_BRUSH));
Rectangle(hdc , 0 , 0 , 100 , 100); // here I should put the size of picture control to clear frame but I dont know how to get its size

//code continues drawing simple stuff...

// release the DC
ReleaseDC(hframe, hdc);
return TRUE;
}