Unique values from SharePoint list as Infopath dropdown

[andreas.zschimmer]

Hi all,

I have read numerous answers on this topic (tried the infopathdev-forum
as well), but the solutions don't seem to work for my situation
(although the examples from the sites work fine!? - arrgh):

I would like to get unique values for my dropdown list from a
SharePoint list.
The dropdown should only contain unique values for the list's column
"Program"

The datasource for the dropdown looks as follows:

my_table_name_on_SharePoint
\- :Course
\- :Trainer
\- rogram <-This is selected as the field entry

For filters I have tried:
not(. = ../preceding-sibling::my_table_name_on_SharePoint/@Program)
not(. = ../preceding-sibling::my_table_name_on_SharePoint/Program)

But somehow it doesn't work. Can someone please help me?
Thanks a lot!

Andreas