You can select folder using FolderSelect() Token API method, see Token API documentation for more information. Formativ wraps most of the tokens for easy to use, see Formativ Language Guide for more information. Code below select work-in-progress folder in GroupWise:
groupwise.FolderSelect("Test HomeWork In Progress")
and show specific message in XXX folder with message ID YYY
If you are referring to select the message but not open message view then unfortunately we think no API methods available to select the message. We recommend you to view/post a message in GroupWise forums for another approach. However, you can open the message view using ItemOpen method below.
call groupwise.ItemOpen("4A0220C8.XXXX.XXXX.100.1697167.1.107B1.1", "")
Hope this helps.