Dear Metalion,
please, can you answer to my question?
(It was for you). 
Sorry but I just saw your message ...
However, NYYRIKKI replied perfectly to your question
Thank you Nyyrikki and Metalion and excuse me, my reply will be later.
I'm very, very busy, unfortunately.
Please, please, wait....
Hello Nyyrikki,
thank you very much for your wonderful explanations.
But I am not an expert.
I used a simple HMMM command and, in Msx-Basic, it could be this:
COPY (2,90)-(255,121) TO (0,90)
It is repeatedly executed.
Please, can you kindly, if it is not too much disturb, show me a little Assembler example with Vdp interrups in order to make smooth my text scroll?
Many, many thanks for your patience.
Yes sure...
In this example I change screen background color, but instead of calculating borders & changing colors I could simply just adjust the screen position and be done with the task.
Thank you Nyyrikki, thank you very much!! 
You and Latok are my heroes! 
Thanks a lot to the others as well. 
I'll try to use those instructions for my scroll.
I hope to succeed....
