Using OpenFileDialog to connect to an Excel Workbook

I have the following code to open an excel sheet

OpenFileDialog dlg = new OpenFileDialog();

DialogResult dlgResult = dlg.ShowDialog();

if (dlgResult == DialogResult.OK)

string conString = System.IO.Path.GetFileName(dlg.FileName);

axMappointControl1.NewMap(MapPoint.GeoMapRegion.geoMapEurope);

MapPoint.Route route = axMappointControl1.ActiveMap.ActiveRoute;

string myConString = @"Provider=Microsoft.Jet.OLEDB.4.0;data source=" +

+ conString + @";Extended Properties=Excel 8.0;";

The code is returning an error for conString, " The name 'conString' does not exist in the current context."

I want to be able to select the excel file from an OpenFileDialog and then use the filename as part of the connection string.

Where am i going wrong with this?

Please help.