prior version definition from property

Dear BPC experts,

I have the version dimension and also the prior version which
is the property of the version dimension:

Version (DM variable)                    Prior version (property of the
                                                       version)

Target version                               Source version

2015_P1                                               2015_FC9

2015_P2                                               2015_FC10

2015_P3                                               2015_FC11

I need a script logic which is able to read the prior version property of the version dimension based on the
DM variable (version) which is the target version. The user will define the
version as a DM variable that will be the target version and the source version
will be the prior version which is the property of the dimension version. Please
be noted that each version has a different prior version.

For example: 

Version=(DM variable)=$VERSION$=2015_P01

Prior version=2015_FC9 (property of the version dimension)

In the script logic I need to define the source data where
the version will be the prior version that is the property of the version
dimension (DM variable):

*XDIM_MEMBERSET VERSION=

Question how I can define the version?

Thanks,