I am extremely alergic to this vine which is growing through my rhody's
It is hard to tell from the picture as we need more info to key a plant out but my guess it is some kind of clematis - maybe clematis virginiana? If you really need a positive ID you can send a sample to the UConn Plant Diagnostic lab. Call the UConn Home & Garden Education Center for directions on sending in a sample. There is a small fee. You also may be able to bring a sample to the Master Gardeners at the Mass Hort Society in Dover. They have a plant clinic during the summer. Or possibly you could bring a sample to a local garden center to confirm the ID.