How Do You Delete (x) Number Of Rows From Database

I am setting up a database which schedules production and tracks inventory of items on a daily basis.  The scheduler may put in 100 identical entries (apart from the identity column) of an item with its corresponding quantity.  My problem is, if there is a shipment of product (a subtraction of quantity from the database), how can I delete a specified number of rows where the inventory listing is 100,000 pcs?  I think the DELETE TOP(r) command will work but I don't know how make the command into an actual variable.  Maybe there is another way too...

My current not-working try;  I look at the product desired to delete, figure out how many rows to delete, and since it is not always an integer, figure out a quantity to add back in.  The addition part works fine but delete command needs work.  Any help is appreciated.

    int InvRows = 0;
    decimal RealInvRows = 0;
    decimal AddQty = 0;
    int preAddAmount = 0; protected void DelInv_Click(object sender, EventArgs e)
    {
        Label TotProdSum = (Label)DetailsView2.FindControl("TotProdSum");
        Label RowQty = (Label)DetailsView3.FindControl("RowQty");

        int SubQty = Convert.ToInt32(ShipQty.Text);

        InvRows = SubQty / Convert.ToInt32(RowQty.Text) + 1;
        RealInvRows = SubQty / Convert.ToDecimal(RowQty.Text);
        AddQty = (InvRows - RealInvRows) * Convert.ToInt32(RowQty.Text);

        IntLbl.Text = Convert.ToString(InvRows);
        RealLbl.Text = Convert.ToString(RealInvRows);
        preAddAmount = Convert.ToInt32(AddQty);
        AddAmount.Text = Convert.ToString(preAddAmount);
       
        for (int r = 0; r <= InvRows; r++)
        {
            forWhile.DeleteCommand = "DELETE TOP (r) FROM Inventory WHERE (Inventory = @Inventory)";
            forWhile.DeleteParameters.Add("Inventory", RowQty.Text);
            forWhile.Delete();
            forWhile.DeleteParameters.Clear();
        }

        forWhile.InsertCommand = "INSERT INTO Inventory(Dte, Product, Inventory) VALUES (@Dte, @Product, @Inventory)";
        forWhile.InsertParameters.Add("Inventory", AddAmount.Text);
        forWhile.InsertParameters.Add("Product", InvProdDDL.Text);
        forWhile.InsertParameters.Add("Dte", Date.Text);
        forWhile.Insert();
        forWhile.InsertParameters.Clear();
    }