I already searched and found several approaches here, but I can\'t get them working for my project.
I want to show an edit page for a list of objects, which should
Assuming you've got the configuration correct - the problem is probably due to the way you're defining the indexing. Try changing the name attribute on the textfield to use
model[%{#rowStatus.index}].datumBis
and let OGNL sort out the access methods. (I'd also use Firebug in Firefox to see what is actually being sent when you submit the form)