<font face="Arial, Verdana" size="2">Assuming you have your setup so that openlp is on monitor 1 and projector on monitor 2 then clicking in the Live window on the slide will regain the focus, and control via OpenLP. </font>
<font face="Arial, Verdana" size="2">Another way (again in Extended desktop or dual screen mode is to to ensure the ppt is saved with presenter view enabled. This then appears (along with speaker notes, and a slide chooser) on the operator screen, and esc will close the presentation and clocking on the Openlp screen will return control.</font>
If for some reason you are not using a dual screen set-up you can exit the power point slideshow without closing powerpoint by pressing esc then clicking back on OpenLP.
Hope this helps