hi Suvakant,
For reading the fields of the webdynpro you can use the Set attribute method for getting the values from the screen fields.
Check the codes:
Data: context_node type ref to if_wd_context_node,
ld_pernr type pernr-pernr.
Retrieve value of webDynpro field
context_node = wd_context->get_child_node( name = 'USER_DETAILS').
context_node->GET_ATTRIBUTE( exporting NAME = 'PERNR'
importing value = ld_pernr ).
Now set the the value from here and update your required field using set_attribute.
Regards,
Sivaganesh