BOB

$(document).ready(function(){
    $("select#src_fld5").change(function(){
        var selectedOption = $(this).children("option:selected").val();
        alert("You have selected the country - " + selectedOption);

        if(selectedOption == 'nominal' || selectedOption == 'book_reff_id'){
                    alert("masuk kondisi");
                         $("#src_val_start5").keypress(function(e){
                                 if (e.which != 8 && e.which != 0 && (e.which < 48 || e.which > 57)) {
        //display error messag
                jQuery('#src_submit').attr('disabled', true)
    }else{

    jQuery('#src_submit').attr('disabled', false)
    }
              });
        }
    });
});