Hi Oliver
The launcherButtonID attribute can be set to the ID of a button only. You could create a button that launches your property page in your property sheet. And then you could add this button's ID to the group's launcherButtonID attribute.
I used the SDK PropertySheet template and here is the code snippet for this:
<group id="LaunchPropertyPage_Group1" caption="Group 1"
appearsOnAddInTab="true" launcherButtonID="LaunchPropertySheet_MyNewPropertySheet_ShowPropertySheet">
...
</group>
</groups>
<controls>
<button id="LaunchPropertySheet_MyNewPropertySheet_ShowPropertySheet" caption="Show MyNewPropertySheet" className="MyNewPropertyPage_ShowButton" loadOnClick="true" smallImage="Images\GenericButtonPurple16.png" largeImage="Images\GenericButtonPurple32.png">
<tooltip heading="Show Property Sheet">Show Property Sheet<disabledText /></tooltip>
</button>
</controls>
</insertModule>
</modules>
<propertySheets>
<insertSheet id="LaunchPropertySheet_MyNewPropertySheet" caption="MyNewPropertySheet" hasGroups="true">
<page id="LaunchPropertyPage_MyNewPropertyPage" caption="MyNewPropertyPage" className="MyNewPropertyPageViewModel" group="Group 1">
<content className="MyNewPropertyPageView" />
</page>
</propertySheets>
Thanks
Uma