CREATE TABLE Sheet1 (F1 char(255), F2 MEMO) 

string sExcelConnectionString = @"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" + pPath + ";Extended Properties=\"Excel 12.0;HDR=YES;\"";
OleDbConnection OleDbConn = new OleDbConnection(sExcelConnectionString);

OleDbParameter parF1 = new OleDbParameter("@F1", OleDbType.VarChar);
OleDbParameter parF2 = new OleDbParameter("@F2", OleDbType.VarChar);

OleDbCommand OleDbCmd = new OleDbCommand("INSERT INTO [Sheet1$] (F1, F2)values(@F1, @F2)", OleDbConn);

OleDbCmd.Parameters.Add(parF1).Value = "текст ...";
OleDbCmd.Parameters.Add(parF2).Value = "текст ...";

OleDbCmd.ExecuteNonQuery();

The field is too small to accept the amount of data you attempted to add. Try inserting or pasting less data.