How to take input from author while starting a workflow



I have a requirement where we need to create a workflow to let authors Move pages from an existing location to a new location. The author will select a page, then go to Timeline to start a new workflow, say MOVEWORKFLOW.

if the author chooses MOVEWORKFLOW from the drop down of possible work flow models, he will be shown text boxes to enter three additional fields:

1. page name in new location

2. page title in new location

3. new path from file picker.

Then he can start the workflow.

How can we customize the Timeline sidebar to have these additional fields? and control them based on the workflow the author selects?