Dynamically graph a chat

This sort of thing usually needs to be done in VBA (or other programming language that can manipulate Excel). I don't know how familiar you are with such programming. Steps I expect:

Outside of Macro:
Create a line chart based on the desired source data range (not A1 and B1 -- a range where the values for A1 and B1 will be put). As values are added to this range, the chart should update.

Within Macro:
1) Store current value for A1 and B1 in 1st row/column of source data range chosen above
2) When data in A1 and B1 change, copy new values into next row/column of chart data range
3) Repeat step 2 for change in A1 and B1

This sort of thing would usually be tied into some kind of event code (change event or calculate event or other event that goes with the changes to A1 and B1). If you are unfamiliar with event procedures, I would suggest that you start with something like this: http://www.cpearson.com/Excel/Events.aspx