[exim] randomize spamscanning- and av-IPs?

Hi,

it is possible to add multiple IPs to the av_scanner- and the spamd_address-settings like this:
spamd_address = 10.10.10.10 783 : 11.11.11.11 783 : 12.12.12.12 783

It seems that the machines always try first 10.10.10.10, then 11.11.11.11 and then 12.12.12.12
I know that I can give priorities via 10.10.10.10 783 pri=10 for example.
But is there a way to randomize how the spam-servers are tried? I have one machine that has always a very high load and the other machines are a bit bored. I could configure another order for each of my mail-servers by hand, but if there would be built-in randomization it would make things easier.

Cheers,
Niels