if (document.images) {
    commercialbuttonup       = new Image();
    commercialbuttonup.src   = "images/commercialbutton.png" ;
    commercialbuttondown     = new Image() ;
    commercialbuttondown.src = "images/commercialbuttondown.png" ;
	residentialbuttonup       = new Image();
    residentialbuttonup.src   = "images/residentialbutton.png" ;
    residentialbuttondown     = new Image() ;
    residentialbuttondown.src = "images/residentialbuttondown.png" ;
	highrisebuttonup       = new Image();
    highrisebuttonup.src   = "images/highrisebutton.png" ;
    highrisebuttondown     = new Image() ;
    highrisebuttondown.src = "images/highrisebuttondown.png" ;
}
function buttondown( buttonname )
{
    if (document.images) {
      document[ buttonname ].src = eval( buttonname + "down.src" );
    }
}
function buttonup ( buttonname )
{
    if (document.images) {
      document[ buttonname ].src = eval( buttonname + "up.src" );
    }
}