Update currency on child record

Dear Friends ,

Please have a look at the below scenario and kindly advise.

Parent entity : Account , Child entity : Amount

There is a 1 : N relationship between Account and Amount, there is a subgrid of Amount on Account form.

When a user clicks on '+' button on subgrid and creates a new Amount record , the requirement is to make the currency of Amount record same as its parent record - Account 's currency so that users will be seeing respective Account's currency symbol on money field in Amount form while creating a new Amount record.

I tried achieving this with the help of a real time workflow on Amount entity which triggers after Amount record creation , but while creating a new Amount record , the currency of the amount record is not updated.Currency is updated only after creation of Amount record.

I want the currency of Amount record to be updated while creation itself so that users will be seeing the updated currency symbol on the money field in Amount form.

Is there a way to trigger a real time workflow before creation of a record ? Or Is there any out of the box way to achieve the above mentioned requirement ?

Thanks,
Naveen