#define MAX_PANELS 500 // ? as many as you need

PANEL* array_panels_d_elemente[MAX_PANELS];
var totalPanels = 0;

if(totalPanels < MAX_PANELS)
{
   array_panels_d_elemente[totalPanels] = pan_create(.....);
   totalPanels += 1;
}



if ( mouse_right && mouse_panel != NULL )
{
    int i;
    for(i=0;i<50;i++)
	{
	    if(mouse_panel == array_panels_d_elemente[i])
              { 
                // panel found do stuff here //
 
                break; // stop the loop
              }            
 	} 
}