Mark document as dirty for derived part updates

[spencer]

Working with a VB.NET addin and I'm stumped how to get a part to be marked for update

Part B is derived from Part A, and I'm making non-geometry changes in Part A.
What I want is for Part B to know it needs to update so the rest of my code can handle the Part B changes on its update, but setting the Part A as dirty doesn't seem to cut it. 

Any good options for doing this?

[GeertvanderHeide]

don't know if you already have the definition of part B, because i don't think there is a link from part A to part B. 

the only link is in Part B, which is reading from part A.

usually when you do it manually, you open a derived part after the original is changed, then update & save and the schanges should be made. 

opening Part B after changes to Part A should already set Part B to dirty. 

[spencer]

Part B does exist, and I know there's no A -> B link but I'm trying to emulate whatever change in part A triggers part B to ask for an update.
Between changing AttributeSet data and setting the A doc as dirty, neither will make part B ask for an update so I'm hoping there's something else to poke at