PSC,
I have tested this in the latest 9.1 release of the OneStream Excel Add-in and I was able to successfully add a new button and configure it to execute a consolidation DM Sequence and it worked without an issue.  In 8.5 are you receiving an error adding the button?  I was initially receiving an error when attempting to add a button and found that it was related to my Excel Trust Settings and set them to "Prompt Me Before Enabling All Controls With Minimal Restrictions" and it allowed me to add the button successfully.  I then executed it and it ran my DM Sequence without an issue.