function valNumBox( curfield ) { 
 
    fieldName   = document.forms[0][curfield]; 
    fieldValue  = fieldName.value; 
    fieldLength = fieldName.value.length; 
 
    var err01   = "Please enter a number."; 
    var err02   = "Please enter whole numbers only."; 
 
    if( fieldValue == "" ) { 
        alert( err01 ); 
        fieldName.focus(); 
    } else { 
        for( var i = 0; i < fieldLength; i++ ) { 
            var ch = fieldValue.substring( i, i + 1 ); 
            if (( ch < "0" ) || ( ch > "9" )) { 
                alert( err02 ); 
                fieldName.focus(); 
                break; 
            } else { 
                // return true; 
            } 
        } 
    } 
}