problem with visible of some label

Hi guys i have a very weird problem, i have 2 labels place in a gridview called instock and out of stock and 1 txtbox call txtqty. If the user enter a value in txtqty which is higher than the actual quantity in the database and he clicks update cart, out of stock will appear. If it is lesser or equal to the actual quantity in database, then instock will appear. But i have a weird bug, for some rows the out of stock label show correctly but for some rows, even when the inputted value is higher than the actual quantity in database, the label still does not switch to out of stock.. please help me

Public Function checkoutofstock(ByVal orderqty As Integer) As Boolean
        Dim boolerror As Boolean
        Dim db_qty ...