Writing Dynamic Action

Dear Team,

Requirement:

Need to write a dynamic action for the below:

a) Whenever a user creates a record in infotype 0014 or 0015 for a specific employee group say for example 8 and employee subgroup 13, the currency field to be defaulted (WAERS) as "USD".

b) Whenever user tries to save the infotype 0014 or 0015 record for a specific employee group say for example 8 and employee subgroup 13, validate the currency field to be USD for this combination and any other currency, need to show an error message with some information.

How can I map the above requirement in a dynamic action. Can we do this.

Your effort and help is appreciated.

Thanks and Regards

Team Member.