how to do a massive search and update

[ik2egl]

I have a heavy log and I have to do a maintenance activity on some old qsos

the first question is: can anyone suggest me what is the best way to do the search:

A) Extract all QSOs in my log , in state WORKED for DXCC challenge, 1) Before a date 2) after a date

the second question is how to perform operation this on a selection:

B) make all selected QSOs in state "not eligible for DXCC challenge"


thanks for the help