I have added some Vba code:
For a userform.
Private Sub UserForm_Activate()
Dim a As Application
Set a = ThisApplication
Dim b As PartDocument
Set b = a.ActiveDocument
Dim Mass As MassProperties
Set Mass = b.ComponentDefinition.MassProperties
TextBox1.Text = Mass.Accuracy
'TextBox2.Text = Mass.AchievedAccuracy(
TextBox3.Text = Mass.Area
TextBox4.Text = Mass.AvailableAccuracy
TextBox5.Text = Mass.CacheResultsOnCompute
TextBox6.Text = Mass.CenterOfMass.X & " " & Mass.CenterOfMass.Y & " " & Mass.CenterOfMass.Z
TextBox7.Text = Mass.IncludeCosmeticWelds
'TextBox8.Text = Mass.IncludeQuantityOverrides
TextBox9.Text = Mass.Mass
TextBox10.Text = Mass.MassOverridden
'TextBox11.Text = Mass.PrincipalMomentsOfInertial
'TextBox12.Text = Mass.RadiusOfGyration
'TextBox13.Text = Mass.RotationToPrincipal
TextBox14.Text = Mass.Type
TextBox15.Text = Mass.Volume
TextBox16.Text = Mass.VolumeOverridden
'TextBox17.Text = Mass.XYZMomentsOfInertia
'LABELS
Label1.Caption = "Mass.Accuracy"
'Label2.Caption = "Mass.AchievedAccuracy"
Label3.Caption = "Mass.Area"
Label4.Caption = "Mass.AvailableAccuracy"
Label5.Caption = "Mass.CacheResultsOnCompute"
Label6.Caption = "Mass.CenterOfMass" ' & " " & Mass.CenterOfMass.Y & " " & Mass.CenterOfMass.Z"""
Label7.Caption = "Mass.IncludeCosmeticWelds"
'Label8.Caption = Mass.IncludeQuantityOverrides
Label9.Caption = "Mass.Mass"
Label10.Caption = "Mass.MassOverridden"
'Label11.Caption = Mass.PrincipalMomentsOfInertial
'Label12.Caption = Mass.RadiusOfGyration
'Label13.Caption = Mass.RotationToPrincipal
Label14.Caption = "Mass.Type"
Label15.Caption = "Mass.Volume"
Label16.Caption = "Mass.VolumeOverridden"
'Label17.Caption = Mass.XYZMomentsOfInertia
End Sub

I have added the Project for VBA too:
load this into your VBA environment.
Regards,
Autodesk Software: Inventor Professional 2018 | Vault Professional 2018 | Autocad Mechanical 2018
Programming Skills: Vba | Vb.net (Add ins Vault / Inventor, Applications) | I-logic
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