Either use the full libray name in the Link Libraries section on the Linker Settings tab, for example:
../../../../thirdparty/boost/lib/libboost_date_time-gcc42-mt.a
or don't use the Link Libraries at all and manually enter your linker settings in the 'Other Linker Options...' window using the -Xlinker. For example,
-Xlinker -Bstatic
-l<some_boost_static_library>
-l<more_static_libraries>
-Xlinker -Bdynamic
-lpthread
-l<more_dynamic_libraries>