[support] Use 1 database for 2 installs

[Roger]

Is it possible to have 2 separate drupal 7 installs accessing the same 
database and can the second install be set to have access to certain 
content fields only but have no data entry permissions?

I ran into a problem some time ago where if modules like workbench and 
others were not installed  the fresh install crashed. Workbench is a 
pain for us.

Reasons I'm asking are:
-- that I need to set up  a newsletter creation and mail out system that 
takes calendar events and dates, locations of events,, quotations,  book 
references and some text content to be used in a view in the second 
installation to out put to the newsletter.

I have tried for days to get simplenews and newsletter working in a copy 
of the original system but there are a huge number of modules in there 
and something is causing the WSOD default to the Stark theme in both 
<Create new content type> and configurations for simplenews.

I did a fresh install of d7.19 on my home system and installed required 
modules for a trial. I find that simplenews and the email systems work 
well as expected.
I'm reluctant to do anything in the original working/live system - I 
reckon some modules don't play nice with others but have no way of knowing.

I would appreciate help on how best to go about this please
thank you in advance
Roger