Re: 'case' requires a constant?

The following code generates the following error:

c:\_DTS_PROGRAMMING\C_PROGRAMMING\vc++\MY_APPS_LAB\XPPLC\WndProc_CW1.cpp(315):
error C2051: case expression not constant

If a value comming from an array that has been defined as below, well,
shouldn't that valuie be constant by default.... I guess not!

The error points to the following line in the code below:

case (WindowButtons[0].CW1_btC_ID): //if equals the exit button

Here is the code:
======================================WndProc_CW1.h
struct hdCW1_WindowButtonsTAG
{
int iCTL_idx;
TCHAR *szCW1_btC_Name;
int CW1_btC_RectLeft;
int CW1_btC_RectTop;
int CW1_btC_RectRight;
int CW1_btC_RectBottom;
int CW1_btC_ID;
};
====================================================

========================================WndProc_CW1.cpp
#include <windows.h>
#include "WndProc_CW1.h" //Default header file

LRESULT CALLBACK WndProc_CW1 (HWND hwnd, UINT message,
              WPARAM wParam, LPARAM lParam)
{
//ARRAY declaration
hdCW1_WindowButtonsTAG WindowButtons[] =
{
1,TEXT("< EXIT >"),580,350,80,40,1,
2,TEXT("SEND BYTES rs232 >"),10,5,180,30,2,
3,TEXT("READ BYTES rs232 >"),20,30,40,50,3,
};

static HWND hdCW1_WindowButtons[3]; //Current 3 window buttons

switch(message)
{
... other code...
case WM_CREATE:

//CREATES MAIN WINDOW BUTTON CONTROLS
for(i=0;i<3;i++)
{
hdCW1_WindowButtons[i] = CreateWindow(
   TEXT ("button"),WindowButtons[i].szCW1_btC_Name,
   WS_CHILD | WS_VISIBLE |BS_PUSHBUTTON ,
   WindowButtons[i].CW1_btC_RectLeft,
   WindowButtons[i].CW1_btC_RectTop,
   WindowButtons[i].CW1_btC_RectRight,
   WindowButtons[i].CW1_btC_RectBottom,
   hwnd,(HMENU)WindowButtons[i].CW1_btC_ID,
  (HINSTANCE) GetWindowLong(hwnd,GWL_HINSTANCE),NULL);
}
return 0;

case WM_COMMAND:

switch (LOWORD(wParam))
{
//error happens because of the next line !
case (WindowButtons[0].CW1_btC_ID): //if equals the exit button
       DestroyWindow(hwnd);
       break;

...other code....

}
===================================================
I can probably do it with an 'if' statement as opposed to doing it by
a case
statement. However, I would like to know why I get a 'constant' error.

Is it because I must declare the structure and array as constant?