At the moment this cannot be done.
The "Sync" process tends to rely on all devices being On all the time.
Often a Mac sat at home is not.
It is either Off completely or is Asleep.
The Sync process is also not very fast and plays out like a speeded up chat.
If the syncing happens as you swap between an iPhone and computer the contact may continue sending new Messages.
The server will tend to deal with these as they happen - mixing them with other incoming sync messages.
Despite the use of Time Stamps the app does not seem to make use of them to "Correct" the order as it goes.
Please, if posting Logs, do not post any Log info after the line "Binary Images for iChat"
iMac 2.5Ghz 5i 2011 (Mountain Lion 10.8.2)
G4/1GhzDual MDD (Leopard 10.5.8)
MacBookPro 2Gb (Snow Leopard 10.6.8)
Mac OS X (10.6.8),
Couple of iPhones and an iPad
"Limit the Logs to the Bits above Binary Images." No, Seriously