[Banknorris]

I had a long seach for this as well and the best I could do was this:

local f = CreateFrame("Frame")
 
f:SetScript("OnEvent",function(self,event,...)
    if event=="PLAYER_LOGIN" then
        self:RegisterEvent("PET_JOURNAL_LIST_UPDATE")
    elseif event=="PET_JOURNAL_LIST_UPDATE" then
        self:UnregisterEvent("PET_JOURNAL_LIST_UPDATE")
        --CALL YOUR STUFF HERE
    end
end)
f:RegisterEvent("PLAYER_LOGIN")