I think you are missing something here buddy. Don't use "on load" to auto run bots, instead, use "/auto" parameter when you open the exe file. For example:
c:\bot.exe /auto
The above Command Prompt/Windows Shortcut command will open UBot bot and auto run it. Btw, I was asking them to load pages when I switch tab, and they said it's impossible, but still...I got it working.