posting a text field message to multiple pre-made text documents

Hi all,

Im trying to create a program that allows me to enter a name into a text field and submit the name into 3 seperate pre-made text files named doc1, doc2 and doc3.

For example: If I were to enter dazbrad into the programme and press submit, doc1, doc2 and doc3 (pre-made text files) would each recieve and add that name to its content.

Furthermore, I would like each pre-made text document to add a seperate suffux to each name that is added. For example, after submitting the name 'dazbrad', doc1, doc2 and doc3 should look as follows:

Doc1 contains - dazbrad1
Doc2 contains - dazbrad2
Doc3 contains - dazbrad3

To further complicate matters, I would like to then go on to add other names at a later point. For example, if I were to later add the name 'brad' to the programme and press submit, the result should be as follows:

Doc1 now contains - dazbrad1 and brad1.
Doc2 now contains - dazbrad2 and brad2.
Doc3 now contains- dazbrad3 and brad3.

If somebody could enlighten me in overcoming this issue, even pointing me in the right direction. Any help would be greatly appreciated. Many thanks in advance.