Hi F.Goncalves,
I believe what Rossano Praderi shared in message 2 is the solution. Thank you Rossano Praderi!
To help more customers, I posted a blog based on this solution. I made some adjustment on the code.
Could you check it and mark message of Rossano Praderi or me as the solution?
http://adndevblog.typepad.com/manufacturing/2016/03/inventor-ilogic-dislay-mass-from-different-lod-o...
core codes:
'get RepresentationsManager
Dim repMgr As RepresentationsManager = ThisApplication.ActiveDocument.ComponentDefinition.RepresentationsManager
'record current LevelOfDetailRepresentation
Dim oCurrentRepName As String = repMgr.ActiveLevelOfDetailRepresentation.Name
Dim oRep As LevelOfDetailRepresentation
Dim oRepName
Dim oMass
For Each oRep In repMgr.LevelOfDetailRepresentations
oRepName = oRep.Name
'activate this LOD
repMgr.LevelOfDetailRepresentations.Item(oRepName).Activate
'get mass
oMass = iProperties.Mass
'update value of custom property
iProperties.Value("Custom", oRepName) = iProperties.Mass
Next
'restore
repMgr.LevelOfDetailRepresentations.Item(oCurrentRepName).Activate