specific libraries for development (not the recent custom libc discussion)

["Rainforestboy" <sensory-transduction@stephen-mcgregor.com>]

Hi

is there either an easy, or any, way to download all the libraries
required for-to build an application, when the libraries are
effectively incompatiable with one's system ?  

By this I mean :
*  a way to get apt, lets say, to know all the libraries required
*  and then get apt, again, to download them specificallly to a
specified,  non-standard directory

As an example, 
wanting to do some work - not as a debian developer, but just for the
project (gnucash, specifically on the DB interface) - 
the version in etch is 2.0.5 - linking to specific libraries 
the development version is 2.2.1 - with many different libraries. 
there is a big difference between the two

I want to 
*  download all the libraries into one directory
*  then set LD_LIBRARY_PATH to that directory when running
and
*  the libraries will generally be in sid (unstable)
*  there are many of them, a gnucash problem
*  the library requirements in turn affect many, many apps
*  I am NOT going to corrupt my system (i.e. go to unstable)

I reckon that many people will have the same problem. I would like to
do some work - and I should, I'm a C++ / C programmer - but how to
get the pile of libraries I want ? (in a working environment)

I also reckon that this problem would have been solved (easily?) by
yourselves.

Could you let me know how ?

thanks if you could 

cheers

Gavrilo