Edited..
Sorry. After reading again you cannot use WHERE on an INSERT statement, loose the WHERE clause or make an UPDATE statement.
INSERT INTO ... WHERE is not a valid query.
If the insert you've posted has correct values and columns, the update should be:
Dim cmd3 As OleDbCommand = New OleDbCommand("UPDATE Tickers SET Quarter_Balance_Sheets = 'Scrapalbe' WHERE Ticker = 'A';", con)
cmd3.ExecuteNonQuery()