I don't think there is a workaround for Entourage.
Entourage 2004 has even less Arabic support.
All in all, you are better using Mail than Entourage.
Entourage seems a little more mature from some aspects.
However, it is a more stable platform.
And Entourage uses a database method where all your mail is in one big file.
This is both dangerous and heavy on the system,and it is an easy way to fill up your disks if you use TimeMachine. If you have a 2-3 GB mail database, it will be backed up (or at least triggered) every mail you get.
As for Excel it works ok with Arabic. The only problem is that it doesn't support RTL sheets (the text inside the cells is displayed correctly).
Apple iWorks is a good platform (410 Dhs).
It has amazing graphics capabilities.
However, Pages (the word processor) is not very strong, and Numbers (the spreadsheet) is different with some advanced features missing.
If all you need is basic writing and simple formulas, it will work fine.
NeoOffice (free) How can you beat that?
It is amazingly strong, and its free!
There are some features that are missing.
And you have to turn it on (for example by loading the word processor) before you can choose which application you want.
But the good thing is that you set it to save in a default format (I use Office's) for your files.
This makes sharing files a lot easier.
Did I mention that its free?