problem to delete more then one row using datagridview checkbox.

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VB

I am using vs 2010.
I have one problem. When I delete more then one row from backend database using datagridview's checkbox it maintains a my field NO in backend.
But suppose, when I delete a row 2 and 4 then it can not maintain a backend. My programming is that when I delete a row then all then getherthan of that rows No field Number is like n=n-1
My code is here. Can anyone solve it?

Dim i, j, n As Integer
       i = 0
       j = 0
       Dim x As Integer = 0
       Dim a(1000) As String
       a(x) = ""
       Try
           While i < DataGridView1.Rows.Count
               If DataGridView1.Rows(i).Cells(0).Value() Then
                   n = DataGridView1.Rows(i).Cells(1).Value()
                   Call openconnection()
                   'Here It Will Delete your Row From The Database Depending On Your Id....
                   str = "DELETE FROM Assets_Detail Where   No=" & n & ""
                   cmd = New SqlCommand(str, cn)
                   cmd.ExecuteNonQuery()
                   a(x) = n.ToString

                   cn.Close()
                   x = x + 1
               End If
               i = i + 1
           End While
       Catch ex As Exception
           MsgBox(ex.ToString())
       End Try
       While j <= Val(a(x))
           Dim temp As Integer
           temp = Val(a(x))
           Call openconnection()
           str = "update Assets_Detail set No=No-1 where No > " & temp & ""
           cmd = New SqlCommand(str, cn)
           cmd.ExecuteNonQuery()
           cn.Close()

           j = j + 1
       End While