The virtual component is defined by a VirtualComponentDefinition. Through the definition, you can also get the information of component settings.
Sub VirtualC()
' assume an assembly document is opened
Dim oAssDoc As AssemblyDocument
Set oAssDoc = ThisApplication.activeDocument
Dim oAssDef As AssemblyComponentDefinition
Set oAssDef = oAssDoc.ComponentDefinition
Dim oMatrix As matrix
Set oMatrix = ThisApplication.TransientGeometry.CreateMatrix
' add one virtual occurrence
Dim oNewOcc As ComponentOccurrence
Set oNewOcc = oAssDef.Occurrences.AddVirtual("MyVirtual", oMatrix)
Dim oCVirtualCompDef As VirtualComponentDefinition
Set oCVirtualCompDef = oNewOcc.Definition
' get BOMStructure
Debug.Print "BOMStructure of Virtual Component: " & oCVirtualCompDef.BOMStructure
Dim oQuantityType As BOMQuantityTypeEnum
Dim oBaseQuantity As Variant
' get QuantityType and Evaluated Quantity
Call oCVirtualCompDef.BOMQuantity.GetBaseQuantity(oQuantityType, oBaseQuantity)
Dim oEvaluatedQuantityType As BOMQuantityTypeEnum
Debug.Print "QuantityType: " & oEvaluatedQuantityType
Dim oEvaluatedQuantity As Double
oEvaluatedQuantity = oCVirtualCompDef.BOMQuantity.GetEvaluatedBaseQuantity(oEvaluatedQuantityType)
Debug.Print "Quantity: " & oEvaluatedQuantity
End Sub