Is it possible to enter our own value in dropdown list box in Module Pool. How?

Dear Experts,

Being new to ABAP, I am trying my hands on Dropdownlist box on Module Pool.

I want to pull data from Ztable(Custom Table) into Dropdown list box on Screen in Module pool and be able to edit it, delete it and enter new data through it, thus thereby able to manage the Ztable. Is it possible in dropdown.

Looking forward for experts advice.

Regards

Deepika