var reentrant = 0, h = 0, b = 0;

function div_blende(id, breite, hoehe, aktion)
{
if( ! reentrant ) {
reentrant = 1;
var move = 0, element = document.getElementById(id);

if( aktion == 'ein' ) {
if(h < hoehe ){ h += 20; move++ }
if(b < breite){ b += 20; move++ }
element.style.visibility = 'visible';
}
else if( aktion == 'aus' ) {
if(h > 0 ){ h -= 20; move++ }
if(b > 0 ){ b -= 20; move++ }
element.style.visibility = (b > 0 && h > 0) ? 'visible' : 'hidden';
}

if( move ) {
element.style.height = h + 'px';
element.style.width = b + 'px';
window.setTimeout( function(){ div_blende(id,hoehe,breite,aktion) }, 20 );
}
reentrant = 0;
}
}