Friday Fun - RunningTotalsAnyone?

If I put this in crystal reports I can manipulate it ok, but actually translating it to a command isn't so easy for me. I'm terrible at cursors and need some help here, pretty pretty please.

I have a table...

CREATE TABLE [dbo].[StagePayment] (
[PaymentID] [uniqueidentifier] NOT NULL ,
[JobID] [uniqueidentifier] NOT NULL ,
[Paid] [bit] NOT NULL ,
[Sequence] [smallint] NOT NULL ,
[Amount] [decimal](10, 2) NOT NULL ,
[Activity] [varchar] (30) NULL ,
[ActivityID] [uniqueidentifier] NULL ,
[DueDate] [datetime] NULL ,
[InvoiceNumber] [varchar] (50) NULL ,
[DueNext] [bit] NOT NULL
) ON [PRIMARY]
GO

Simple example of the data I need to work with...

PayIDJobIDPaidSequenceAmountDueNext

609412110.000
6B1E 18110.000
297C 25110.000
E175 30114390.000
8CF9 30124390.000
916839114400.000
59F4 39126632.000
BCAF 5411417.500
59225402417.500
8DA0 68112988.000
76C5 68129958.000
0C13 68137566.000
F3F4 68142390.000

What I need to accomplish is flagging the DueNext field if the amount due has not been paid. I cannot rely on the Paid field as it's currently user controlled. I need to compare what's due with the total already paid (stored in another table).

So for instance,
Job #68 - the total amount due would be $22902.00

If the customer has paid $15000.00 then Sequence 3, PayID 0C13, should be flagged as DueNext.

Anyone have a very simple example of a running total cursor that I can reference or a better idea of how to work with this? I appreciate any and all suggestions!
Thanks!
abbra_doo