Addition of new fields to structure

Hi All

1)i want to add few fields to existing structure RFC_VIQMMA which is used in bapi - IQS4_CREATE_NOTIFICATION(I_VIQMMA_T).

I would like to know after addition of fields in structure, can I see that whenever I execute that bapi manually and populate values for those fields manually??

2)All these additional fields will be optional fields for that structure. Whether it will affect other programs which is already using that structure??what precautions should i take?