You need to use MID(<the string>, <thestart>,<howmanyletters>)
This will work if the string always has (for example) 18 letters before the items you want.
If not, you need to be more devious.
You would have to search for the first occurence of the '.'
with Instr(<thestring>,"."

That will tell you what position the '.' takes.
Subtract 3 from that, and then use MID()
e.g:
Mid(<thestring>,instr(<thestring>,'.')-3,12)