Auto generate serial number

New FormJJ - Copy.xlsb

I have used searchable suggestion dropdown list in B2. As you can see, if I type branch name in B2 it automatically appears in C2. There shouldn't be a dispatch to all the 44 branches on the same day, its depends on the daily bases. It various and it can't be on ascending orders, such as it could be any from the list of branches.

Now my question is,

With having a key as a date (B3) and branch name (C2), I want the serial number (SL.NO - in A2) to generate automatically against branch name.

E.g.., Firstly, In A2 I will give a unique serial number (5545 for Bangalore). Then If I Choose Ahmedabad, I want the serial number to generate automatically to (5546).

Again, its depends on the daily bases branch, I will not know which company I will be choosing.

Regards

Silambu

please help someone

You should have to explain it little bit more
or
Use Visual Basic