Run project server workflow via webservice

Hello!

I have developed workflow for Project Server 2010. At certaing point this workflow has to wait at one stage submit button has to be disabled,

I have used OnProjectCommit activity to achieve this. At this point this workflow must be pushed to next stage only by some WS call. I thought that RunProjectWorkflow method (http://msdn.microsoft.com/en-us/library/gg207838.aspx) is capable of doing something like this. But apparently not. Probably I will have to trigger OnProjectCommit event somehow but I do not know how?

What are my possibilities to run workflow via WS? 

Any hints?