How to update an infotype field if a field is updated in another infotype

Hi Gurus,

I am new to sap. I need a help in coding to the following requirement.

There are two infotypes one basic infotype --- 008 and other is infotype --- 057

If an updationg for the hourly data field (one of the field in 008) is updated by Hr then there should be an automatic update in one of the field in infotype 057 based on small business logic.

I heard that there is user exit or badi to any infotype. I dont know which is that user exit or badi for the field in the 008 where I can add my logic.

Can any one guide me how to do this?

Thanks

Ravi