function CheckForNum()
// 1) get value
// 2) validate value
// 3) if value fails validation, display error and return false
{
    var msg = '';   // initialize error message variable

    // ****************************************************************
    // 1) get value
    var txtChargeTotal = document.getElementById('chargetotal');
    var valChargeTotal = txtChargeTotal.value;

    // ****************************************************************
    // 2) validate value
    // 2.1) check for no value; if yes, return
    if ((msg == '') && (valChargeTotal == '')) { msg = 'Please enter a donation value and try again.'; }

    // 2.2) check for valid number; if no, return
    if ((msg == '') && (isNaN(valChargeTotal))) { msg = 'Please enter a valid dollar amount and try again.'; }

    // 2.3) round and pad value appropriately
    if (msg == '')
    {
        valChargeTotal = Math.round(parseFloat(valChargeTotal) * 100) / 100;
        txtChargeTotal.value = valChargeTotal;
    }

    // ****************************************************************
    // 3) if value fails validation, display error and return false
    if (msg != '') { alert(msg); return false; }
}