Duplicate records inserted

I use the following code in a after successful login event:
Sub AfterSuccessfulLogin()

'** Insert a record into another table ****

strSQLInsert = "insert into Tracking (Username, Updated) values ('" & Session("UserID") & "', now())"

dbConnection.Execute strSQLInsert
End Sub
It is pretty straight forward, but sometimes the record is inserted into the table twice. What am I doing wrong?
Thanks,
Jerome A. Wendell