Setting GWT_HOME variable

hello,

i have a beginner question!

i have imported the smartgwtee showcase and want to build it! in my buildpath i have set a variable GWT_HOME to my gwt-sdk! but when i try to build, this error appears:

...workspaces/eclipse_workspace/ShowcaseEE/build.xml:30: 
Warning: Could not find file ..../workspaces/eclipse_workspace/ShowcaseEE/${env.GWT_HOME}/gwt-servlet.jar to copy.

thank you!