Frankly, here's your main problem straight away

Fax? Tell your client it's the 21st Century!
OK, now I've got that off my chest: what you want to do can almost certainly be done in Excel, but it won't be the easiest way. Doing it in Access instead will alkmost certainly be easier, and work better. So, if you've got Access, find someone who can use Access properly and get them to set this up for you.
If you don't have Access, then it'll be trickier to do, but it's certainly possible. The first question is does your client have Excel? If they do, you can create an order template in Excel for them to fill out which can then be linked into a master Excel spreadsheet, and you can use a variety of methods to pull the data in.
If they don't have Excel, pretty much anything else you try to do is going to be more complicated and long winded than just using a manual system, frankly...
