Dynamic addition of fields to internal table

Hi all,

I have an internal table itab_data with some fields in it.

I need to add few more fields to this internal table during run-time based on some conditions. All the fields to be added is of same data type . But the number of fields vary based on input.

Itab_data contains

matnr type mara-matnr

maktx type makt-maktx.

Now, based on input i need to add few more fields of type AUSP-ATWRT.

The field names are like atwrt1 , atwrt2...atwrt n ..

Hope my question is clear..

Thanking you in advance ..

Shankara Narayanan T.V