hi anwesha,
for tmg editor do upto step 2.
then,
3.in tmg,environment->modification->events
4.form routines will be opened in that.
5.in first column (T) put 05 and form routine <formname>.
6.in next column editor click,it will ask for include,just create it.
7.in that include just write your code
for example:
FORM check.
IF ZPP_DR19_1-PLANT is INITIAL.
MESSAGE 'hi' TYPE 'E'.
ENDIF.
ENDFORM.
and activate.
if any problem let me know,i will share screenshot.