var winNueva 
function PopUp(prmtrURLPagina, prmtrNombrePagina, prmtrWidth, prmtrHeight)
	{
	var intLeft = (screen.availWidth - prmtrWidth) / 2
	var intTop = ((screen.availHeight) - prmtrHeight) / 2
	var strUrl = prmtrURLPagina
	var strNombrePagina = prmtrNombrePagina	
	var strParametros = "toolbar=yes,location=yes,directories=yes,status=yes,menubar=yes, "
	strParametros += "scrollbars=yes,copyhistory=no, resizable=yes, minimize=yes, maximize=yes," 
	strParametros += ",width=" + prmtrWidth + ",height=" + prmtrHeight
	strParametros += ",left=" + intLeft + ",screenX=" + intLeft + ",top=" + intTop + ",screenY=" + intTop
	winNueva = window.open(strUrl, strNombrePagina, strParametros)
	//winPrelatic.focus()
	if (winNueva != null && (winNueva.closed != true))
		{setTimeout('winNueva.focus();', 10);}	
	}