Convert VBA to DateDiff calculation query

You can't convert an expression into a query. A query has multiple records. However, if you're asking how to put the expression into a query so you get the calculation for each record in the query, it's straightforwards. Replace the Me.<etc> with the actual field names in your table. For example:

Overdue: DateDiff("d",[DateReceived],Now())

and:
AmountDue: IIf([Overdue]>30,[Amount]*0.02/30*[Overdue],0)

Okay, so, by your example, I would need the following fields: Overdue, DateReceived, AmountDue, Amount
Moreover, are you saying that these two strings go into the criteria of different fields, and if so, let me know if I figure right:
Overdue: DateDiff("d",[DateReceived],Now())    ----- goes into the Amount field criteria
AmountDue: IIf([Overdue]>30,[Amount]*0.02/30*[Overdue],0)    ----- goes into the DateReceived field criteria

I'm very new to this, so could you please elaborate?
Many kind thanks in advance,
John

No, they don't go into the criteria - they actually go into "Field" row, as they are calculated fields (in other words, new fields in the query that get their values based on other fields).

Hmmmmnnn....I'll be trying it out. Wish me luck! :-)

Any problems, don't hesitate to post back!

Thank, you shanesuebsahakarn. It's working. Is there a way to format it in currency--or should this be in another question?

You're a really great guy! Thank you very much, shanesuebsahakarn!

No probs, glad I could help :)