DECLARE RandomUser_CURSOR CURSOR
LOCAL FORWARD_ONLY KEYSET SCROLL_LOCKS    
    FOR
    select *
	from TableA
	where @bCustom = 0
	union all
	select *
	from TableB
	where @bCustom != 0
    FOR UPDATE
    OPEN RandomUser_CURSOR
    FETCH NEXT FROM RandomUser_CURSOR INTO    
              @Col1, @Col2, @Col3
    WHILE @@FETCH_STATUS = 0
            BEGIN

order by
case
  when @Orderby = 'Account' then Account
  when @Orderby = 'OrderDate' then cast(OrderDate as int)
end