Hi,
to retrieve cell format using GetOleDbSchemaTable you might use OleDbSchemaGuid. If you check it out will see a whole bunch of information that can be gathered from it.
Code below demonstrates this approach.
OleDbConnection conn = new OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=c:\\YourFileName.xls;Extended Properties=Excel 8.0");
conn.Open();
DataTable dt = conn.GetOleDbSchemaTable(OleDbSchemaGuid.Columns, null);
dataGridView1.DataSource = dt;
dataGridView1.ReadOnly = true;
conn.Close();
Run this code and look for a column called "DATA_TYPE". If you have some values in percentage, for instance, will see the value 130 which represents this kind of format.