' Get the top-level assemby.
    Dim AsmDoc As AssemblyDocument
    AsmDoc = ThisApplication.ActiveDocument

    Dim RefDocs As DocumentsEnumerator
     RefDocs = AsmDoc.AllReferencedDocuments
    
    ' Iterate through the docs
    Dim Doc As Document
    For Each Doc In RefDocs
        ' Look for part documents.
        If Doc.DocumentType = kPartDocumentObject Then
            ' Look for a specific param
            Dim Params As Parameters
             Params = Doc.ComponentDefinition.Parameters
            
            On Error Resume Next
            Dim Param As Parameter
         Param = Params.Item("G_L")
                ' Set the custom property format.
                Dim PropFormat As CustomPropertyFormat
                PropFormat = Param.CustomPropertyFormat
                PropFormat.Precision = kZeroDecimalPlacePrecision
                PropFormat.Units = "mm"
				PropFormat.ShowUnitsString = True
                PropFormat.PropertyType = kTextPropertyType
            End If
    Next