It would be a more optimum design to NOT use repeating fields here, but to use a related table of records in a portal where each portal row replaces one of your repetitions of these repeating fields.
but if you want entering data into a given repetition of Bid Number to record the current date in the corresponding repetition of Bid Date:
If [ Not IsEmpty ( bid cost::BidType_Number [ Get(ActiveRepetitionNumber) ] ) ]
Set Field [bid cost::BidType_Date [ Get(ActiveRepetitionNumber) ] ; Get ( CurrentDate ) ]
... or without any trigger and script, you can make the BidType_Date a calculation field, result date, with calc:
trigger = bidtype_number ;
Get ( CurrentDate )
thanks - the BidType_Date as a calculation works really well.