Hi Neo,
Is it still possible to call an external dll ?
Yes. TS has a "DLL Extension Kit" that can incorporate any DLL written in C or C++
Are signals evaluated tick by tick or at bar's end ?
In realtime, the signals are evaluated tick by tick, so if you just want to automate your system, you will get the signal "as it happens". For backtesting, there is a setting called "backtesting resolution". It can be set as low as one minute. So, if you are testing a system on 10 minute bars, the signals can be updated within the bar to 1 minute accuracy. At that point, TS has several assumptions of how the bar traded based on the relationship of the open, high, low and close, just as it did in older versions of the program.
Orders for BUY STOP or SELL STOP do they work on the same bar or only next bar ?
The systems I'm working with only use next bar orders, mainly because I find them more robust (I like to know I can fall asleep waiting for a signal and still be profitable with a later entry, lol

) However, I think in realtime they will update tick by tick or if backtesting, it will use the backtesting resolution I described above. However, you may want to shoot an email to them first to be sure since I haven't tried it.
I don't think you can keep global variables though...
maybe just keep variables value from one call to another call ?
If by global variables (I am not a programmer) you mean that the variable can be called by multiple functions or systems, then I don't think so. I always have to define each variable for each new system. But my expertise here is very small. I can create/call functions that simplify tedious formulas (like common technical indicators for example). I am fortunate to have a great friend and trading partner that is an excellent programmer and has answered 3 trillion questions from me in the last week since I got TS Pro. While I have done basic EasyLanguage in the past, I would have a much longer learning curve without his help. I will ask him and reply to this thread if I find out anything different.
I was using metastock before this and have had to make slight adjustments, although easylanguage is much more complete than the MS formula language. As Neo mentioned, the easiest way to learn it is to open up a sample indicator or system and look at the code. I do a lot of copy and pasting, lol.
I am a TS owner so I could get that price. others might use the trick mentioned above maybe.
For the record, I really do own supercharts and don't recommend anyone to lie.

Its just that they never asked for proof...
J-Trade asked earlier about a user group for TS. There may be one out there, but I don't know of it. However, there is a mail list that has a lot of useful stuff (along with a lot of worthless stuff typical of mail lists, lol). There is an archive of these messages updated each day at:
http://purebytes.com/archives/omega/
Also, the support at TS has been extremely responsive. I get answers to emails in less than a day.
Hope this helps.
Kirk