Transaction Notification For User Defined Object

Dear Expert,

I want to create a transaction notification for my user defined form. I have a matrix on my form which has a field as 'Code'. I want that this field (On Row Level) should have unique values all the time while adding or updating the form.

Object Type: MaterialMaster

Table Name: MaterialDetails

FieldName: U_Code

Plz help me to get this notification.

Regards