is there a way to add to a number in a database. For example the field in the database is for example 5, instead of inserting over it adds to it. Lets say the user selects a number from a pop up which in this case is 3 rather than overwriting the exsisting data php or sql adds the 3 to the five to give a new figure in the database of 8. This would also need to work for negatives.

Any ideas/advice?