I have 5 buttons on the screen. When I click on button 1, I want to read the scripts from
C:\GuiXT\Button1
When I click on button 2, I want to read the scripts from
C:\GuiXT\Button2
... and so on. 
Is something like this possible?

There is currently no elegant solution, since &V[...] variables are not supported in script directory names. As a workaround, put an

Include  C:\GuiXT\buttonV[scriptsubdir]\scriptname.txt

in each GuiXT script, and set

Set V[scriptsubdir] "1"

when the user clicks button 1,

Set V[scriptsubdir] "2"

when the user clicks button 2 and so on.

In the included script, use a "Stop" command at the end so that the "normal" script is not executed.