I have replied to this entry, because, for some reason I don't understand, if I reply to your latest entry, I am
automatically logged out.  I tried this multiple times, and also on many other entries and had no issues other than
entry 69787 - any reason for this, Stefan?

Anyway, what about MOptions? That appears to do what your example, and needs two lines in elog.cfg file:

Moptions WaferID = 1001, 1002, 1003, 1004, 1005
Extendable Options = WaferID

I've done a couple of quick tests on a test logbook I keep for such experimentation, and it appears to do all 
you have asked of it.  I added a new option 1006.  However, I found that one has to add that new one on its own, 
let the entry become proper, and then edit the entry to add the other, existing, values.   If you tick entries and 
also add a new one, then your new entry is all those listed on their own, that is you would get and new entry
in the config file such as "1002 | 1004 | 1006", rather than just 1006

This is probably an result of an unexpected use of Moptions and extendable options, rather than a bug per se.

> Hey, 
> 
> thanks for your answer. I completely get your point. However, I think my question as not precise enough.
> 
> I would like to have a numeric input, but many at the same time. When I make a new post, I would like to have an attribute 'wafer_IDs' that specifies the list of wafers this process has been performed with. So for a single post I would like to have a list like this:
> 
> wafer_IDs = numeric value, numeric value, numeric value, extendable
> 
> Note: I am not referring here to the option. The numeric values are freely chooses numbers, the only this that varies from post to post is the number of numeric values put.
> 
> Let me make an example (If the attribute were a string this would be the equivalent):
> 
> 1st post: A process that was run with 3 wafers (ID: 1000, ID: 1001 and ID: 1002):
> wafer IDs = 1000, 1001, 1002
> 
> 2nd post: A process that is run with 2 wafers (ID: 1000 and ID: 1002):
> wafer IDs = 1000, 1002
> 
> The string solves the issue, but is not as nice as having directly a list of integers.
> 
> Thanks for your help!
> 
> Best,
> 
> Nick