Search Criteria set to AND or OR user preference

Hi
What I am trying to do is allow the user to set the search preference to either AND for all options or OR for all options. Do you know the best way to do this?
Possible Options:

1) Set up 2 DA Server Behaviours Searches on a results page 1 set to ANDs and 1 set to ORs- if so how do you do this and have it pick the right one when finding the results.

2) On Search Page radio button one set to choose AND and one set to OR and through coding all "comparison list additions" are updated to the appropriate AND or OR.

3) Put 2 buttons on the search form or something similar, one going to a results page that contains Server Behaviour DataAssist Search set to AND and the other to a second results page that contains Server Behaviour DA Search set to OR.

Not sure which option if any would work and if one of them does, have you any idea what code I should use?

Hope this makes sense.

I am using php, WA Super Suite on a local server XAMPP using MySQL and Apache.

Thanks Jo