about the harvinb post,
if I put this in the gallery.Items property :
and I type something into the textinputBox, the gallery does show me the results based on ALL the Office365 Users,
and not only these 100 results showed from the gallery, but still, if you leave the textinputBox empty it will still show only 100 results.
Last thing, I don't think it will help that much, but making a label with this formula in its Text property :
"Row number -> " & CountRows(galleryName.AllItems)
will show the number of rows that the gallery is currently showing
Hope it helps
In case you haven't seen this, you can change the call to SearchUser and provide it with a top parameter to get up to 999 users.
If you have more users than that, @Shanescows has an example of how he accomplished this in a production app by building a custom control. Here is the link to that: