You'll need the UPDATE
-Statement which
creates an update query that changes values in fields in a specified table based on specified criteria.
Syntax:
UPDATE Your_Table_Name
SET Total_Stocks = Total_Stocks + @IncrementValue,
WHERE Stocks_Name = 'Beef';
You'll need to add an Parameter to fill @IncrementValue
yourOleDBCommand.Parameters.Add("@IncrementValue", OleDbType.Integer).Value = Convert.ToInt32(yourTextBox.Text);
Source: MSDN