Hola, esto es lo que tengo en el aspx:
<asp:HyperLinkField HeaderText="INFORME" Text="Informe" DataNavigateUrlFields="COD_OFICINA,NOMBRE_OFICINA" DataNavigateUrlFormatString="OFICINASDetailsINFORM E.aspx?COD_OFICINA={0}&NOMBRE_OFICINA={1}" />
y esto en el aspx.vb:
Public Sub setImageURL(ByVal src As Object, ByVal e As GridViewRowEventArgs)
If e.Row.RowType = DataControlRowType.DataRow Then
Dim myCells As TableCellCollection = e.Row.Cells
Dim planLink As HyperLink = DirectCast(myCells(myCells.Count - 1).Controls(0), HyperLink)
planLink.ImageUrl = "~/Imagenes/aspneticons/print_16x16.gif"
End If
End Sub