add value to kvstore only if its not empty

[angelinealex]

Hi,
I have couple of questions.

    .........
    eval fieldname=....
   | outputlookup my_kvstore_lookup

1. How to add fieldname value to kvstore only if fieldname is not null/no empty. When its empty it shouldn't add to the kvstore.

2. Another question is, can I add a value to kvstore in the middle of the saved searches? Because at the end of saved search I have to summary index the data.

Looking for some urgent help.
Thank you.