Fields with mixed string/number data

I am using ADO.Net to extract data from a table in an Excel workbook.
Some of the columns are a combination of text and number data - the text
"n.a." when there is no measurement for that point and a number when
there is a measurement. When ADO gets the data the numbers are ignored,
treated as blanks. It's those numbers I need!

Here's the code.


cn = New System.Data.OleDb.OleDbConnection _
("provider=Microsoft.Jet.OLEDB.4.0;" & _
"data source=" & WorkbookFileName & _
";Extended Properties=Excel 8.0;")

Dim cmd As OleDbCommand = New OleDbCommand _
("select * from [WorksheetName$] where IsDate(Time) _
order by Time", cn)

cn.Open()

Dim dr As OleDbDataReader = cmd.ExecuteReader



Thanks in advance,

--
Peter Aitken
.