Dynamic Query Grid Results

I have a Dynamic Query which populates in a grid based upon a partial search of the PO Num.
When the proper PO Num Row gets highlighted I want a text box to fill with a column entry from the grid.

I have created an After Row Activate Event on the Grid. I am unsure of the proper code to get the text box to equal a column from the grid.

//Order - PONum Leave
	private void txtOrderHed_PONum_Leave(object sender, System.EventArgs args)
	gridPOResults.Visible = true; //Show PO Grid
	numOrderDtl_OrderNum.Value = (0);
	numOrderDtl_OrderLine.Value = (0);
	numOrderDtl_TotalReleases.Value = (0);
	epiTextBoxPORefNum.Text = txtOrderHed_PONum.Text;
	DynamicQueryAdapter dqa = new DynamicQueryAdapter(oTrans);
	QueryExecutionDataSet qeds = dqa.GetQueryExecutionParametersByID("GS_Order_Detail_ParamsPO");
	qeds.ExecutionParameter.AddExecutionParameterRow("POParam", epiTextBoxPORefNum.Text, "nvarchar", false, Guid.NewGuid(), "A");
	dqa.ExecuteByID("GS_Order_Detail_ParamsPO", qeds);
	gridPOResults.DataSource = dqa.QueryResults.Tables["Results"];

//Order - PO Grid Refreshes Text Box
private void gridPOResults_AfterRowActivate(object sender, System.EventArgs args)
		epiTextBoxPORefNum.Text = "cab123456";     //This is just hard coded right now because I have no idea how to say column "OrderHed_PONum" from the grid. 

UltraGridRow activeRow = (sender as EpiUltraGrid).ActiveRow;
var yourVal = ActiveRow.Cells["Your Col Name"].Value.ToString()
//yourVal now has you value, set it whereever you like
SomeTextBox.Text = yourVal;