<img id="excelimg" alt=Excel onclick="javascript:toExcel()" src="excel.BMP"/>

function toExcel() {
    document.getElementById("excelimg").disabled=true;
    document.getElementById("excelimg").alt="Please wait till your previous request is processed!";
    document.getElementById("excelimg").style.cursor="default";
    var excel="excel";
    var location1="<%= baseUrl %>Print?"+param;
    excelWindow = window.open(location1,"_excel","height=400, width=600,scrollbars=yes,status=1, menubar=1,toolbar=0,menubar=1, resizable=yes");
    excelWindow.focus();
    excelWindow.attachEvent("onbeforeunload",disableExcelIcon);
}
function disableExcelIcon(){
    document.getElementById("excelimg").disabled=false;
    document.getElementById("excelimg").style.cursor="pointer";
    document.getElementById("excelimg").alt="Excel";
}