I want to include some dynamic part in the filename of the msi file my wix projects produce. This dynamic part should be controlled by variables which are part of my wix project
The msi file name is not determined by your wix files, but by the light.exe -out switch. You can use the same value for -out and inside your wix files if you do the following in your build script, assuming it is a batch script:
set
productversion=1.2.3-out foo%productversion%.msi to the
light.exe linker$(env.productversion)