'From https://www.cadlinecommunity.co.uk/hc/admin/articles/203069922
Try
oHoldingPositionName = InputBox("Specify the    N A M E    of the new iProperty", "Cadline Community - iProperty Name", "New")
oValue = InputBox("Specify the    V A L U E    of the new iProperty", "Cadline Community - iProperty Value", "1")
iProperties.Value("Custom", oHoldingPositionName) = oValue
Catch

End Try