inclusind a new field in internal table

Dear All,

I am a newbie to abap world.

I wish to clarify if there is some way like

data: itab like mseg

In addition to the mseg table structure i want to add a new field to same.

I tried something like

data: itab like mseg,

field like transparenttable-field.

but it doesnot work.I want i should be able to refer itab-field without any compilation error.