This is a slightly enhanced version of the XML. The label statement and screentip statement are redundant, only one is needed.
Code:
<mso:customUI xmlns:doc="http://schemas.microsoft.com/office/2006/01/customui/currentDocument"
xmlns:mso="http://schemas.microsoft.com/office/2006/01/customui">
<mso:ribbon>
<mso:qat>
<mso:documentControls>
<mso:separator idQ="doc:sep1" visible="true"/>
<mso:button idQ="doc:RunSpellcheck_1" visible="true"
label="Run Spell Check"
screentip="Run Spell Check"
supertip="Run Word's spell check in this protected form."
imageMso="TagMarkComplete"
onAction="modSplChk.RunSpellcheck"/>
<mso:separator idQ="doc:sep2" visible="true"/>
</mso:documentControls>
</mso:qat>
</mso:ribbon>
</mso:customUI>
That added a "supertip" and is the one that is
here.