How to use EXECUTE interrupt?

Hi Markus,
Thanks for explanation.
In fact,you are really frank.(That's what I appreciate indeed).
The piece of code you see is not written by me.
The coder of this snippet of code had claimed that
every one could use this code to patch a program which is running.
So I decided to use this method and see if it's possible and doable.
Now,you say that I should run this code in Ring0.
So I just don't know how to switch to Ring0 when I'm in Ring3 executing and
running my program in which this snippet of code is implemented.
I hope there is a way to switch to Ring0 and apply the patch to the running program
and then come back to Ring3.
If so,let me know how.

As for the first part,I want to ,make a file with Overlay.
That's why I asked about EXECUTION INTERRUPT.
What I understood from your post is that something like the following code should do the task.

.DATA

FileName BYTE    'a.txt',0
Ptrfn      DWORD FileName

.CODE

lds dx,Ptrfn

Let me know if I have made a mistake.

Best Regards,
Zest.