Work with Path

http://stackoverflow.com/questions/428085/how-do-i-set-a-path-in-visual-studio
For example, to prepend C:\Windows\Temp to the PATH:

PATH=C:\WINDOWS\Temp;%PATH%

Similarly, to append $(TargetDir)\DLLS to the PATH:

PATH=%PATH%;$(TargetDir)\DLLS

Project | Properties | Select Configuration | Configuration Properties | Debugging | Working directory
Repeat for each project configuration.