installer in silent mode doesn't work

because our installer is for upgading our software. It requires the installer should run in silent mode.

I trid to those command lines
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SilentInstall silent

function .onInit
SetSilent silent
functionend
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But it doesn't work. I have added two custom pages with 3 checkbox (default is checked)?
How can i do?

Check with IfSilent into custom page's show function, set the default values for all 3 check boxes and skip to custom page's leave function.