Bug 305036 [Path Variables] Minor API changes in Dynamic Path Variables area
I'm attaching a patch illustrating what should be done in this area.
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/internal/ide/dialogs/PathVariablesGroup.java
private void updateWidgetState() {
    	variableTable.refresh();
        updateEnabledState();
    }
    /**
     * @param resource
     */
    public void setResource(IResource resource) {
    	currentResource = resource;
        if (resource != null)
        	pathVariableManager = resource.getPathVariableManager();
        else
        	pathVariableManager = ResourcesPlugin.getWorkspace().getPathVariableManager();
        removedVariableNames = new HashSet();
        tempPathVariables = new TreeMap();
        
        initTemporaryState();
    }
	/**
	 * Reloads the path variables from the project description.
	 */
	public void reloadContent() {
        removedVariableNames = new HashSet();
        tempPathVariables = new TreeMap();
		initTemporaryState();
		if (variableTable != null)
	        updateWidgetState();
	}
}