Hi RAM,
Hope you requirement is to force the user to input data by only selecting values from OVS help. i.e. user is not allowed to enter inputs manually but he can select values from OVS
Here, by restricting user from being manual input, you are not allowing user to key in the valid input also.
Only thing, you have to do is check whether the input is valid against your search help records. because user can also manually key in the valid input right? so why to restrict always
So, the validation of input data should meet your requirement and if any invalid data found, throw an error message and do not proceed further.
To validate the input of select options, please refer the below document:
Highlighting select-options in red in Web dynpro ABAP
Note: in above document the validation logic written in ONCLICK event handler method, but you move code into WDDOBEFOREACTION( ) method
Hope this helps you.
Regards,
Rama