Pass a value from client area to custom provisioning module

[teqnick]

I need to pass a value from client area to my module function. I have extra input in client area template

 

<form method="post" action="clientarea.php?action=productdetails">
<input type="hidden" name="id" value="{$serviceid}" />
<input type="hidden" name="modop" value="custom" />
<input type="hidden" name="a" value="DoSomething" />
[b]<input type="hidden" name="foo" value="bar" />[/b]
<input type="submit" value="Do It" />
</form>

 

But when it comes to _DoSomething(array $params) function there is no any $params['foo'] or anything similar. How I can pass the variable to use it value in my module?