[nerv_]

как понял

function Show( objId, hBlock )  {
	var obj = document.getElementById( objId );
	if ( obj.offsetHeight < hBlock ) {
		obj.style.height = ( obj.offsetHeight + 5 ) + "px";
		setTimeout ( function(){ Show( objId, hBlock ) }, 10 );
	} else {
		obj.style.height = "auto";
	}
}