delete mail from mailbox if over 300 or older than 80 days

[luke@xxxxxxxxxxxxxxx]

Hi,

I've now moved to mutt for mail, yay,
but now,
how do I delete individual messages.

I'd like to set it up so that: if there are more than 300 messages in a 
mailbox, delete those that are oldest (probably 300+ depending on how they are 
sorted).
I'd like to delete messages that are older than (now-80days).

Is there an easy way to do this with mutt internally?

thanks,
Luke