Its an additional programming for a standard or Z program.
Check the thread User Exit / BADI
Know more about badi and user exit, please search in SCN and read.
The coding/programming done via an ABAPer.
Its about a development..
If you want to go for a development, then write your requirement as a FS.
Then share your thinking with your ABAP team.
He will do that.. He will hide the field..
You can do this via screen variant using SHD0..
But it will be little tough..