You don't need the subexpression $()
in this case:
"${env:ProgramFiles(x86)}\ProgramFolder\Executable.exe"
Outputs:
C:\Program Files (x86)\ProgramFolder\Executable.exe
If you still want to use a subexpression, you can specify a variable name that contains PowerShell syntax characters like so:
"$(${env:ProgramFiles(x86)})\ProgramFolder\Executable.exe"