Bug 273489 [Mac] We should not nest sheets
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/internal/ide/dialogs/PathVariableDialog.java
if ((variableType & IResource.FOLDER) == 0) {
			folderButton.setEnabled(false);
		}
        folderButton.addSelectionListener(new SelectionAdapter() {
            public void widgetSelected(SelectionEvent e) {
                selectFolder();
            }
        });
    }
    /**
     * Fires validations (variable name first) and updates enabled state for the
     * "Ok" button accordingly.
     */
    private void variableNameModified() {
        
        variableName = variableNameField.getText();
        validationStatus = IMessageProvider.NONE;
        okButton.setEnabled(validateVariableName() && validateVariableValue());
        nameEntered = true;
    }
    /**
     * Fires validations (variable value first) and updates enabled state for the
     * "Ok" button accordingly.
     */
    private void variableValueModified() {
        
        variableValue = variableValueField.getText().trim();
        validationStatus = IMessageProvider.NONE;
        okButton.setEnabled(validateVariableValue() && validateVariableName());
        locationEntered = true;