Calculation Criteria On Max(date)

My query selects all those who donated to a fund.The max on the date restricts all but their last donation, working fine.But now I want to list all those who have not donated anything in the last x days (user defined). I want to use Date()- dateField>30 but now it does not let me peform the query.
Any way I can do this in just one query? Thanks!

SELECT main.dgTitle, main.dgInit, main.dgSurname, main.dgNo, main.dgStreet, main.dgShul, Max(main.dgDate) AS maxdate
FROM main
WHERE (((Date()-[main].[dgdate])>30))
GROUP BY main.dgTitle, main.dgInit, main.dgSurname, main.dgNo, main.dgStreet, main.dgShul;