I've been using different instances of a single form class as a main data entry form, as a child form and as a picklist form. From the menu, the form is a main data entry form. From a child form class, a called form is a child form. It changes to the data session of the calling form. As a child or picklist form, I loop through the data environment to open views that are not already open. This code happens in the data environment's OpenTables method.

So, yes, you can switch the data session even as the form is instantiating.