I will join a conference in Stockholm this November for 7 days can i visit France using Swedish visa?

I am a Filipino citizen and will be attending a conference in Stockholm for 7 days this November 2011. The Swedish coordinator will grant us only seven days ( only during the duration of the conference) stay in Sweden. I together with my friends want to visit France, Italy, Spain and Prague after the conference which will take additional 7 to 10 days extension. Will the Swedish embassy grant us the additional 7-10 days extension of our visa? or do we have to apply for another schengen visa to the countries that we will visit like France. My relatives from France are inviting us and willing to sponsor us. I f Swedish embassy will not grant us the 7 days extension where will our sponsor from France address their letter of invitation? Will it mean we will have to get 2 schengen visas? Thanks Liza