Hi Brian,
At the moment, Smart Search:
http://help.qlik.com/sense/2.0/en-US/online/#../Subsystems/Hub/Content/Search/use-search-tool.htm
Does not support searching via expressions such as Margin > .20 etc. or Sum(Sales) < 100 etc. This is something we have discussed, but I am not sure of its current state.
You CAN search with the smart search tool AND then append selections and searches with other objects to narrow down the result, but it is not an all in one approach using the search tool.
NOTE: Chart objects can provide restrictions such as this, but need to be defined in the object itself:
(click to enlarge)

Now List Search boxes can use expressions in their search option:
http://help.qlik.com/sense/2.0/en-US/online/#../Subsystems/Hub/Content/Search/data-search.htm?Highli...

Let me know how you do.
Please mark the appropriate replies as CORRECT / HELPFUL so our team and other members know that your question(s) has been answered to your satisfaction.
Regards,
Mike Tarallo
Qlik
Regards,
Mike Tarallo
Qlik