Scheduling a project based on a task start date

I am trying to find a way to choose a task in a project, set a date for it and then have the project schedule from that date.

I know how to do it in MS Project 2010... support.microsoft.com/kb/113447

You set the task's constraint type to "Must Start On" and then flip the project to "schedule from finish" and flip it back to "schedule from start". Sadly, I read there is no way to update PROJ_INFO_SCHED_FROM property in the PSI when a project is already created... So I am a bit stumped on how to go about this.