The follow exert will explain how to obtain the values from a datagridview cell double click.
do you need to be able to update the database from the user form or to update the displayed values in the datagridview?
Private Sub DataGridView1_CellDoubleClick(sender As Object, e As System.Windows.Forms.DataGridViewCellEventArgs) Handles DataGridView1.CellDoubleClick
Dim CellValueA As String = Nothing
Dim CellValueB As String = Nothing
CellValueA = DataGridView1.Rows(DataGridView1.CurrentRow.Index).Cells(0).Value.ToString
CellValueA = DataGridView1.Rows(DataGridView1.CurrentRow.Index).Cells(1).Value.ToString
Dim ofrm As New Form2(CellValueA, CellValueB)
ofrm.show()
End Sub