First let me say I am new to sharepoint workflows. Having said that, here's my question:
I need to create a workflow that fires when a document is added to [po request] document library. The workflow is a basic approval of a purchase request. If the request is approved, the task approver will approve the task. I would also like for the task approver to provide a Purchase order # and have the workflow update a column in the document library with that Purchase order #. I was thinking of doing this by defining a workflow variable and then using that variable in a custom task to receive the purchase Request number from the user. Then I would like to be able to update a site column [PO Number] with the value of the purchase request number. Any ideas on how to do this?