Security Alerts pops up with "Program Signed By: - No Signature"

We have inserted computed subform by using Notes API in _Calendar Entry form. After that when we try to schedule meeting. Security Alerts pops up with “Program Signed By: - No Signature”. If we look in designer we get “Modified By” as current user.

If we try through designer we don’t get security alerts.

What changes are required so as to remove those alerts in code?

Subject: Security Alerts pops up with “Program Signed By: - No Signature”.

who can help me?