blueprints with multiple templates; how to set the selection ?

[iamgoingtosneeze]

I've a blueprint that allows the user to select which template to use from a list.- say 'template a', 'template b'  I would like to use the create-from-template macro to bring up the wizard, but have a specific template selected.

i.e. i have a button with create-from-template b. and when it goes into the wizard 'b' is selected.

on another page i have a button with create-from-template a. and when it goes into the wizard 'a' is selected.

I could of course have a completely separate templates, but we have 10s of different document types and I don't want to flood the blueprint selection UI. Instead I want to have a blueprint to categorise them. However in some situations I would like to give the user of the convenience of pre-selecting the document. 

I would guess I do something in the post-render . Is there a way i can find out what page i am on ?

Thanks in advance, Laura