To gain another 2nd rounder, what the Fins could do is switch 1st rounders with the team lying at 22 (currently Baltimore Ravens) and pick up their 2nd rounder in the process.
Going by ESPN's draft pick value chart, Miami's pick is valued at 1200. The Ravens 1st at 22 is worth 780 and their 2nd rounder is worth 360 (Miami could actually still get another 5th or 6th rounder out of that type of trade).
It then all depends on a couple of things though. The Ravens need a WR and the only wideout worth trading to 12 for would be Dez Bryant. For that to happen Bryant would have to be the number 1 guy on their board and that they feel he is worth trading up for.
If Miami have someone like Dan Williams as the highest guy on their board who is available and they feel they could still get him later, then the trade has potential to happen.
That type of trade is certainly possible, but needs alot to happen also. There is actually alot of things Miami could do if they are willing to trade down. I just used the Ravens at 22 as an example.