In order to localize a search, use the SSR search zone. Tutorial 10 and Tutorial 22 discuss the SSR Search Area options. Tutorial 10 illustrates the SSR Window Search Area, while Tutorial 22 illustrates the SSR Polygon Search Area.
See the related page in the Online Help for more information on how the SSR Search Area option works. Note that there is also the option of an SSR Exclusion Area, which works exactly like the SSR Search Area, except that rather than choosing a search area, you are excluding an area from the search. You can define multiple SSR Exclusion areas if necessary, but you cannot define both SSR Exclusion Areas and SSR Search Areas in the same model.
Tutorial 10: SSR Window Search Area
Tutorial 22: SSR Polygon Search Area