UML: state diagrams.

[cwarrior]

I am being asked to create a state diagram for an invoice which is created, filled in as you see appropriate, and completed for the purchase of a vehicle.
So, I understand what a state diagram is. A state diagram is used to model states of an object and the events causing state changes. A state diagram consists of states and transitions.

The problem is I do not see how creating an invoice and filling it up has any states?
I have written this much and it doesn't make any sense to me.
[waitingforcustomertodecide]----------customerdecidestobuy---[creatinginvoice]-----????

I mean would writingModel or writingCustomersname or writingVehicleCost be states? and if so, how would I transition from one to another one? what would the events be?
would it be like [writingModel]------doneWritingModel---->[writingCustomerName]?

[jbking]

Let me preface this by saying I never took UML in school and this is merely some suggestions. Creating an invoice should be a state, right? That there is an order form generated with order number or other criteria before a user fills out the form. Then what are the parts of an invoice,e.g. customer address, customer license information, vehicle description/identification, tax calculations, payment details like total due and date?

Another way to look at this would be to write out in pseudocode what are the steps to be done to result in a completed invoice and each of those represents a state.