Auto update 'summary tab' with 'detailed tab'

[Salman]

E.g.: Summary tab is showing:

Customers No Customer Name:
AA1111 ABC
BB2222 DEF
CC3333 GHI

And then few new customers are added on the system which I can export to a
separate tab (Detailed tab). Now I want the above summary tab to pick any new
items been included in my revised/updated detailed tab. If there are no new
customer, the summary tab should remain unchanged and add if there are any
new customers, as soon as I update the detailed tab - the summary tab should
automatically be updated with any new customers (but should not delete any
old customer which are in my summary tab and not included in detailed tab
anymore).
E.g.: The revised detailed tab:

Customers No Customer Name:
BB2222 DEF
CC3333 GHI
DD4444 JKL

ie AA1111 has been disappeared in my detailed tab (which I still want to
appear on my summary tab). DD4444 has been added as new customer (which I
also want to include in my summary tab).
Ie: My summary tab should look like:

Customers No Customer Name:
AA1111 ABC
BB2222 DEF
CC3333 GHI
DD4444 JKL

Thanks