Hi Richard.
Sorry. I jumped into your discussion at the end when I posted my response. I just went back and read your scenario. I believe that you have a much more difficult situation here.
(following, dd will stand for 'drop-down'):
The problem is that when you refresh the web service with the dd2 selection, you are refreshing it for ALL dd3's. That means than the selections from any previous dd3 have been updated to the selections on your current row. This is a problem. That means if you have 5 rows, and on the 5th row you make a selection in dd2, the web service is updated and dd3 is populated. But then go back to dd3 on rows 1-4 and you'll find the same list for all 5 rows. Whoops!
This, unfortunately, is a restricting design flaw. The only way around it is to redesign.
Here's what I recommend (but don't know that it's possible because I don't know how the backend of you web service works):
If possible, dd3 should be bound to a secondary data source (can be web service still if you want) that pulls down ALL the related data to any possible selection in dd2. That means if dd2 can be A, B or C, then dd3 needs to be able to pull A {1, 2, 3}, B {4, 5, 6}, or C {7, 8, 9}. I.E. dd3 will populate with 4, 5 and 6 if dd2 is B.
The dd3 data cannot keep changing like it currently is. There has to be static data on the back end with some kind of a link to tie dd2 and dd3 together. Thus the dd3 data might be flat and look something like this (two columsn per row):
A, 1
A, 2
A, 3
B, 4
B, 5
B, 6
C, 7
C, 8
C, 9
Or it might be hierarchical and look simthing like:
A
1
2
3
B
4
5
6
C
7
8
9
But it must have values representing those in dd2 as well as the choices for dd3 that tie to the dd2 values.
The big switch here (and I don't know that you can do this -- it won't be so nice if you have something like 100,000 rows or something) is that you have to have a static data source to work with for DD3, not dynamic like it is now.
This would be entirely different if the cascading list was NOT in a repeating table. Then you wouldn't have this problem.
Good luck!
Greg Collins [InfoPath MVP]
InfoPath Dev