Get sheet metal flat pattern face and perimeter

I am looking for a way to get the sheet metal flat pattern face and the perimeter of that face.

So far I have the code to put the part in the flatten state.

Set swDocExt = swModel.Extension

'get Flat Pattern feature

boolstatus = swDocExt.SelectByID2("Flat-Pattern1", "BODYFEATURE", 0, 0, 0, False, 0, Nothing, 0)

'put in flatten state

swModel.SetBendState 2

boolstatus = swModel.EditRebuild3

'return to bent state

swModel.SetBendState 3

boolstatus = swModel.EditRebuild3

Now I just need to figure out how to select the face and get the perimeter. 

Dim instance As IMeasure

Dim value As Double

value = instance.Perimeter

SolidworksApi macros