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I want to make a component/plugin/whatever that will allow clicking on a word which would display all articles with this word in its "metadata keywords".  Kind of like a tag function, but using the metadata.

Now, I think the best way to do this is not to create a sperate component, but rather instruct the existing search engine to only search in the metadata keywords fields and then in my specified way. 
I thought "no problem" at the beginning, it's just writing a searchbot (after some browsing around for 2 hours..), but "Oh no!", I forgot one basic thing:  How can I tell the standard search component (the fill-in form for it) to ONLY use my searchbot and no other?  Or even better, how can I make it so that next to the standard searchbox I can add the dropdown option "Only search in keywords" ?  Or even better than better, why not allow a dropdown that allow this option for every searchbox (e.g. "only search in contacts", "only search in category x", "only search in keywords", etc..) ??

Any help MUCH appreciated!!  (P.S. This is for a volunteer site to get Technology to the poor http://www.tec4dev.be )

Well, I guess it isn't possible.
I did it without integrated search page, but as an apart component after all 

Check here: KeywordSearch