Mohan,
I can't see your code you have written.
Why don't you use the functionality in the characteristic maintenance to default a value? Transaction CT04 - on the tab 'values', check mark the value in the column with the header 'D' (default value).
In case you really need an object dependency: A procedure like this - linked to the characteristic CORE_DIA or to the configuration profile of the material - should do the trick:
$SET_DEFAULT ($SELF, CORE_DIA, 100)
Regards
Stefan
