Dear Ashwin,
I think you have to enhance WD /SAPSRM/WDC_UI_SC_DOTC_BD.
The problem is that the field ITEMS_TABLE_DESCRIPTION_LINK_L which is the description field is not a input text field.
I think you can add a custom field as input text and copy the material description when the SC is saved.
I dont think you can do it for SC items with material code but yes for free text.
Regards,
Martin