How to set my own variable in [Setup] and read it from [Code] - inno-setup

Question

I'm trying to create a script in Inno Setup to pull files from a GitHub repository, extract it, and write it to a directory defined in the [Setup] section.
[Setup]
MyVariable={userappdata}\MetaQuotes\Terminal\{#MyAppName}
[Code]
procedure CurStepChanged(CurStep: TSetupStep);
begin
// Copy the selected files to the selected directory
if not FileCopy(Output + '\file1.txt', MyVariable + '\file1.txt', False) then
begin
MsgBox('Failed to copy file1.txt to the selected directory.', mbError, MB_OK);
Abort();
end;
if not FileCopy(Output + '\file2.txt', MyVariable + '\file2.txt', False) then
begin
MsgBox('Failed to copy file2.txt to the selected directory.', mbError, MB_OK);
Abort();
end;
end;
Obviously, this won't compile because MyVariable hasn't been defined in the Pascal script. Only, I'm not sure how to reference the value in [Setup]. Or am I going about this in the wrong way?

Answer 1

Well, you can read the [Setup] section directives with SetupSetting preprocessor function:
How to read a [Setup] parameter in the Pascal code?
But you cannot invent your own new directives.
But you can either:
Use preprocessor variable using #define directive (the way you already use it for MyAppName):
#define MyVariable "{userappdata}\MetaQuotes\Terminal\" + MyAppName
It does not matter where you place the #define as long as it it before you use the variable.
Use it like this in the Pascal Script:
ExpandConstant('{#MyVariable}\file1.txt')
The ExpandConstant is to expand the {userappdata}.
Use Pascal Script constant:
[Code]
const
MyVariable = '{userappdata}\MetaQuotes\Terminal\{#MyAppName}';
Use it like any other Pascal Script variable/constant.
ExpandConstant(MyVariable) + '\file1.txt'