I own a small mail order company and at the moment I am compiling
customer details on excel databases. Some customers are on duplicate
databases and all need to receive letters every 14 days and the letter
depends on where the customer started in the sequence. It is all
becoming quite a headache and I need to automate the process to
produce one report a day so as I know which of the many different
letters I need to send to who. I understand there are specialist
programs for mail order companies to handle such tasks although can't
find them on the net. I am not refering to general database manegement
programs but I need one specific to mail order and list management. A
list of possible programs would be required of which I can choose
which best suits my needs.

seach for "freeware".  These are software programs that are given free
for a period of time.  The programs are very inexpensive.