make a special monitoring between midnight and midnight

[mma]

Hi all !

I have a mail server with a number of mails received, rejected and accepted by minute. These values are monitored normally by SNMP.
I would three graphs with the sum of mail received (for example) for one day (since midnight to midnight).
Is that possible ? I make an item as sum(PFreceived,86400) but It uses last values of 24 hours...

the algorithm would :

while true
{
    
    if (time() = midnight) 0<-nbofmail_received
    nbofmail_received<-nbofmail_received+nbofmail_received_per_minute
    print nbofmail_received
    sleep(60 seconds)
}

But I would use zabbix and not a script on my server...