Your client is probably inserting something that contains an ' like O'Brien.
Since a ' has special meaning in SQL, this breaks things. The fix is easy: just replace a single ' for two before you send the data to the database. E.g.:
promocode = Replace(promocode, ".", "''")
Note that this is only a short term fix. Google for "SQL Injection" to learn why this is not only a client's nuisance, but also a thread to your application and server. Instead, you should look at solid escaping techniques / validation routines and parameterized queries. You need to use the Parameters collection of the Command object to add new parameters and provide their values.
Imar
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Imar Spaanjaars
http://Imar.Spaanjaars.Com
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