Since there are no multi-value drop-down boxes in InfoPath I have a
drop-down box in a repeating table so that users can select more than
one choice.  What I would like to do now is make it so that when the
user selects one value, in the next drop-down box that value is removed
from the drop-down values - i.e. I want to make it so users can not
select the same value more than once.  I have a feeling that this is
possible using X-Path and filters, but I am lost when it comes to that,
so any help would be very much appreciated.

Thank-you!