[O] Change default org file to file note to.

[Richard Riley]

I have an org template 

,----
|                             ("j" "journal" entry (file+datetree "journal.org")
|                              "* %?\n\t:PROPERTIES:\n\t:DateCreated: 
%T\n\t:Link: %a\n\t:END:\n")
`----

How could I go about altering this or approaching the problem in a
different manner in order to have the first journal entry I create be
defaulted to journal.org but any further ones using the last file logged
to?

Use case:

I start work and hit C-c c j to create a journal item. Its a general
"journal" so journal.org is ok ..  "hangover this morning". I then
stretch my arms, yawn and open up files for project X. I then create a
new journal entry ("Must fix issue A for projectX") but hit C-c C-w to
write it to ProjectX.org/journal instead of journal.org. I then want all
further journal entries (using the template and default key above) to
default to ProjectX.org/journal since thats the project I'm working on.

Possible? I understand I could have a specific key sequence with no
target file and I suspect that would default to last file/section but I
really want this to stick with the journal sections of hte last project
journalled to.