Manually decrease space between notes

[TorbjörnBjörkman]

Hello,

Since this is my first post on Lilypond I start with: Thanks for a great 
program! *insert applause here*

On to my question:
Is there any way that I can manually decrease the space between notes? I only 
want to decrease the space between two specific notes in one place.

Alternatively (and a better solution to my actual problem):
How can I define a new type of notehead consisting of two baroque style 
breve's really close together? It is a kind of longa note that is common in 
baroque music as a long final note.

Cheers
Torbjörn Björkman