The search object is a bit irrelevant to this issue, it's more of a display thing and I'll explain.
You can use a conditional rule on the object you wish to display for one region only.
In the chart properties go to General tab, then go to calculation condition and type:
Meaning, only display the chart if one region is selected.
How can the user select? either by a list box, or by a search object as you wanted before.
Hope it helps,