Validation on Report as finished Journal

Good Morning,

I need to validate RAF Journal at the time of validate.

1.i have added one field 

The validation is if that field is not filled then at the time of validate the system should check and throw error that the particular field is not filled.

I have placed code in Class ProdJournalCheckPostProd.CheckTrans()

it works fine. when i click validate from RAF Journal.

But when i change status for Production Order from Released to Created.

The system will create New RAF Journal and Automatically will post that New RAF Journal.

Here my error comes.Because the field is not filled manually.

It is posted by system Automatically when Status of production order is reset.

The validation should not trigger when i change Status..

How can i achieve this.

Please have some light on this.

Regards.