Hi Gunnar,
What version of LabVIEW do you use? Something new in LabVIEW 2013 is the "Open Dynamic Bitfile Reference". With this, you could use e.g. an "Application Directory" node and build the path at runtime:
http://zone.ni.com/reference/en-XX/help/371599J-01/lvfpgahost/open_dyn_bitfile_reference/