@AjaySrinivasKumarY There are sevaral ways in which you can achieve this requirement.

Approach 1 :

-Use pyGUID as the primary key to the table.

-Run a utility after the approval step ,

      -Be sure to construct new instances of your concrete Data class

     -Do a property-set on details that needs to be saved.

     - Perform Obj-Save with Write Now option enabled. 

This will save a new record to the table.

Approach 2:

- Use OOTB functions to set primary key followed by Obj-Save

        - round(random(1,10000)) - this will create a random number between 1 to 10000

        - pxGetUniqueID() - this will create a random number

Approach 3: ( Use if the key needs to be in an incremental way)

- Use Obj-Browse to fetch the resultcount of the table and increment it with +1. Save the incremented value to the customerkey property

-  Perform Obj-Save with Write Now option enabled. 

Let me know if this Helps!