mm01enhancement

hi sap guru's,

please help me regarding mm01 enhancement i.e

in mm01 screen i was added new sub screen with one field material description of lenth 100 char,

and i was append A STRUCTURE in MARA,

structure contains field material description ,

my mm01 subscreen field name is MARA-ZMATD.

after entering material description in mm01 i am unable to

GET THAT DATA IN MM01.

i was entered my coding in functional module

EXIT_SAPLMGMU_001 i.e exit given for mm01.

now please help me how to insert data into backend table ,

in which table i need to append structure,

and what coding i need to use,

thanks & regards

prasad