Also guessing here...
I would;
1) Get the datagridview datasource (preferably as a DataTable)
2) Iterate columns or rows.
Dim dataTable As DataTable = TryCast(dgv.DataSource, DataTable)
For Each column As DataColumn In dataTable.Columns
For Each dRow as DataRow in dataTable.Rows
TextBox1.Text = dRow[column]
Exit
Exit
You will have to do a lot more debugging, but this is the jist of it IMO.