How to set parent path $ (SRCROOT) in Xcode

From http://developer.apple.com/library/mac/#documentation/DeveloperTools/Reference/XcodeBuildSettingRef/1-Build_Setting_Reference/build_setting_ref.html%23//apple_ref/doc/uid/TP40003931-CH3-SW38 we can find the settings Xcode assemblies such as $ (SRCROOT). But in my case, the header files are in the parent folder $ (SRCROOT). Is there a way to access this without sending an absolute path?

Thank!