IF you have set this reference this is a way to use it (Early binding):

Code:
Dim Ph As PhotoshopApplication
    Dim Dr As IAutoPSDoc
    
    Set Ph = New PhotoshopApplication
    Set Dr = Ph.Open("C:\MyDrawing.psd")
As far As i can see it's extremly limited exposure of the features of photoshop so don't expect much.
Maybe CS(2) offers more