One time run of a conditional update of a field

Does anyone know if its possible to do a one time conditional update.  

Ie I have 2 dates.  I want to update the second date (date2) (ie add 7 days to it) but only the first time that Date1 is updated.

I can find a workaround using hidden fields, but though Id ask if there is a quicker/easier way.

Thanks

Hi,

Conditions will always be triggered when changes are made to a field.  There is not currently a way to limit them to trigger a single time.  If a field is set to update based on a date field and add 7 days, each time the date field is changed, the second field will update with date+7.