Panorama 6 had a linked clairvoyance feature under which clairvoyance wouldn’t offer unique values based on prior entries to that field, but rather based on prior entries in some other field, either in the same database or in another, open, database. This is not yet implemented in Panorama X although I believe Jim intends to implement it someday.
How to work around its absence is going to vary depending on your specific circumstances. If there is sufficient information in your invoice DB to reliably narrow the price list DB options down to just one entry, then one of Panorama X’s many lookup functions (check its Help, and also the Lookup Wizard under the Help menu, for details.) But if you need the user to pick from a list of possible price list DB entries lookups alone can’t finish the task.
What I’ve done in such cases is open a form on which a Text List Object lists the possible values when an user choice is needed, set up so that clicking a TLO line puts that value into your invoice DB and closes the TLO form. Populate the TLO using
arrayselectedbuild( to generate a list of possible values based on your known invoice DB values. If there could be duplicate copies of possible values in your price list DB, you can further shrink that list with
arraydeduplicate( which also sorts its output as a side benefit. Depending on how many possible values will be listed you may wish to enable scroll bars for your TLO or add a search box to the form so the user can further shrink the list. It’s not as elegant as linked clairvoyance was, but it works reasonably well, quickly and even mostly via the keyboard. A basic setup can be made fairly quickly (start with the Construct menu). I did find myself doing much tweaking of the size and positioning of the TLO forms and the various options available.