How can I test if a menu tree item exists before clicking it

I am working with a SysTreeView32 object. The tree structure in this object will change dynamically so I want to test if the menu item exists before r-clicking it. There is no "exists" property for items inside this control. What is an efficient way of testing if an item exists before clicking it?

'This is what I am trying to do in VBS

myItem = "|root|sub-item|childItem"

if myMenuTree.wItems.item(myItem).exists then 'Object doesn't support this property or method

  call myMenuTree.ClickItemR(myItem)

else

  log.error("The item did not appear in the menu tree")

end if

This link doesn't give any clues that I can see