function alertUser(id)
{
    //alert("FUNCTION: alertUser");
    //alert("id = " + id);
    var df = document.forms["form"];
    var doc = document.form;

    if (df.elements[id].value != "")
    {
        df.elements[id].value = "";
        df.elements[id].focus();
        alert("The Seat must contain a letter for the row identifer\ne.g 22A");
        return false;
    }

}

seat_zelle.innerHTML = "<input type='text' id='specify"+s+"' name='specify"+s+"' "+
                       "title='Insert Seat Number for Pax: "+ passagier + " " + passNo + " / Segment "+ parseFloat(s+1) +"' "+
                       "class='selects' size='5' onBlur='if(!/^.*[a-z].*/i.test(this.value)){alertUser(this.id);};     concatSeats(this.value,"+passNo+",this.id,"+pass+");' "+
"onKeyUp='this.value=this.value.toUpperCase(); return IsNumeric(this.value,this.id);' />";