Cell A2 holds a value of $100. Cell A1 is a cell used when an expense is made. So, say we spent $10. I want to enter $10 in cell A1 and have cell A2 automatially update to $110. Or, i'd just like to be able to type over the $100 in cell A2 with $10 and have it know to add $100 + $10 to give me $110.