I need help in developing a mathematical model to describe the equivalent resistance of a 2 dimensional resistor array.  My high level math skills are quite rusty.   

The array can be visualized as a number of individual resistors arranged in a horizontal and vertical grid.  The horizontal resistors are all the same value and the vertical resistors are all the same value.  The resistance would be measured at the two corners on one side of the rectangular grid.

I also need to calculate the effect that removing one or more elements of the array would have on the equivalent resistance.  The changes to the array could be individual or clusters of resistors and could be anywhere in the array.

My goal is to get these equations in a form so that I might utilize a spread sheet to predict the equivalent resistance of different array sizes with different resistor values.  I would also try and use the spreadsheet to determine each array elements relative value to the equivalent resistance.

Any suggestions on how to do this would be greatly appreciated.