Create A/B Testing program in Responsys

Hi all:

I want to create a program to test two campaigns, so we can decide which one is better.

In this case, I create an initial filter with the audience I want to send to (for example, 1,000 contacts). Then, I create a switch so 50% will be send 'Campaign A' and 50% will receive 'Campaign 2'.

My problem is that, for each campaign, I have to define a filter; but, I do not want to do it, because it has to be 500 contacts in each path, depending on the switch. The graph is somehting like this:

and this is the question, with the switch I want that standard email campaign is sent to 50%, and personaliz email campaign is sent to the rest. But, in this case, which filter do I have to define in each campaign? I do not want any filter.