Hey Gabor
I have one suggestion I can think of that might help. You could add a new property to the contact class like "CurrentMAOrderID" with an integer representation and make it not visible in editing form. To add this field you would go to Modules application, Contact Management > Classes and edit the OM_Contact class. Click the fields tab and add a new field. You can leave this null by default and make sure you uncheck show in editing form.
Once you have created this new field, you can go into your automation process and in the beginning of the automation process add a "Set contact property" and set this newly created property to the appropriate order id, maybe something like Contact.Orders.FirstItem, this way you have it as a "variable" and can use it whenever you need it. The only bad thing about this solution is if you need to start this automation each time a customer orders a product then it will obviously overwrite the existing ID, but maybe you can think of some way around this limitation