Add Special Char to input value

I have a list range like below:
Starting Ending
------------ --------
000000 099999
100000 219999
220000 479999
480000 629999

When I input 099998 value in a cell , I want automatically add 1aa in front of 099998 and PAT end of 099998.
When value 099998 entered , it must be 1aa09998PAT automatically in cell.

And other values will come as below


Add Between Add
---- ------------ ---------
1aa 000000 ... 099999 PAT
1ab 100000 ... 219999 PAT
1ac 220000 ... 479999 PAT
1ad 480000 ... 629999 PAT

How to make in a macro?