Formula Filling Problems

[obnoxs32]

I have tried using the auto formula feature as you can see in the attachment below. I would like to be able to just enter in the Payment Made column and let excel do the rest... If I chose not to make an extra payment do I need to put 0 in that column or is there an "IF THEN" statement I can use?

I also tried formulas in the original balance column but it filled in some figures that are not correct. How can I put in formulas and fill down the column without calculating it until a figure is entered?

Any help would be greatly appreciated... As you can tell from the time on this post... I have had enough tinkering around aimlessly in excel help tab!!!

[Bob Phillips]

Goto Tools>Options>Edit and check the Extend data range formats and formulas box.