Inserting at a particular position in an itab

Hi all.

Have a internal table as follows:

TYPES:BEGIN OF gty_kopfitab,
 MATNR TYPE mara-MATNR,
 maktx TYPE makt-maktx,
 MTART TYPE mara-MTART,
 loekz TYPE stko-loekz,
 datuv TYPE stko-datuv,
 compMatnr type mara-MATNR,
 compmaktx type  makt-maktx,
 warengruppe type mara-matkl,
 ERSKZ type stpo-erskz,
 posnr type stpo-posnr,
 menge type stpo-menge,
 ME type stpo-meins,
END OF gty_kopfitab.

types: tt_kopfitab TYPE TABLE OF gty_kopfitab.
data gt_kopfitab type tt_kopfitab WITH HEADER LINE.

After I have filled the "gt_kopfitab" I have to insert some new lines at a particular position in the internal table.

For Eg.- If the internal table has an entry as follows, I have to insert some more lines after the following line OR "MATNR" in the internal table.

MATNR maktx MTART POSNR CompMatNr

2100030931 EPS/PDF/Liz. Col.C WVF 0010 2100027625

How could I do that.

Thanks

K