Kill process before (re)install using "taskkill /f /im" in Inno Setup

I found a way using the BeforeInstall parameter and a simple Pascal Script function in the code section. I added a string parameter so it can be reused for multiple processes.

[Files]
Source: "My Service 1.exe"; DestDir: "{app}"; Flags: ignoreversion; \
    BeforeInstall: TaskKill('My Service 1.exe')
Source: "My Service 2.exe"; DestDir: "{app}"; Flags: ignoreversion; \
    BeforeInstall: TaskKill('My Service 2.exe')

[Code]
procedure TaskKill(FileName: String);
var
  ResultCode: Integer;
begin
    Exec('taskkill.exe', '/f /im ' + '"' + FileName + '"', '', SW_HIDE,
     ewWaitUntilTerminated, ResultCode);
end;

Unless the installer is running on a Windows XP machine, or you have set CloseApplications directive to no (the default is yes), the installer should close the application automatically:

The functionality is available since Inno Setup 5.5 on Windows Vista and newer.

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Though sometimes yes is not enough, you need to use force:
Installer created via Inno Setup, can't close applications during installation on Windows 10