Dim pMxDoc As IMxDocument
Set pMxDoc = ThisDocument
Dim pMap As IMap
Set pMap = pMxDoc.FocusMap
Dim pSR As ISpatialReference
Set pSR = pMap.SpatialReference
Dim pPolygon As IPolygon
Dim pArea as IArea
Set pPolygon = [Shape]
pPolygon.Project pSR
Set pArea = pPolygon
Output = pArea.area