public static void Exec(MercatorUi.MovableControls.MovableButton clickedButton)
{
    // enter your customized code here

    MercatorUi.Forms.Billing.BillingForm billingForm = (MercatorUi.Forms.Billing.BillingForm)clickedButton.Form;
    if (!billingForm.BillingEngine.ReadOnly)
    {
        billingForm.BillingEngine.ChangeAllItemData();
        billingForm.BillingEngine.ChangeAllPrices();
    }
}