PositionReport alternative for Fix4.2?

Imported from previous forum

We have a fix engine that talks with a provider via the Fix4.4 standard. For one of its features it relies on receiving the PositionReport (35=AP) message back from the server. I’m trying to clone this project for another provider which uses Fix4.2, and everything has been moved over except the feature requiring the PositionReport. The only information I really need is to know from a message is when to update my positions (maybe this is done via the executionreport message in 4.2?) and a way to be able to calculate the LongQty and ShortQty values (704 & 705 in 4.4). So far I’ve not seen any way to do this, any one have any ideas? Thanks.