Is it possible to add/subtract in one cell, and have it subtract/add in another cell that already has a value?

Question

Is it possible to add/subtract in one cell, and have it subtract/add in another cell that already has a value? I am thinking it may be a if function but I can not wrap my head around how I would write out the formula.

Answer 1

Let's say you have 2 columns B and C that already contain data. And if you Add a number to B you want that number to be subtracted from C.

My recommendation is to write a macro that will work as follows:

First the user selects the two columns and then runs the macro

For each row
    Cell c = getCell("C" + row);
    double cval = c.Value;        
    c.type = FORMULA;
    c.Formula = "=" + (cval + getCell("B" + row).Value) + "-B"+row;
    c.Recalculate()

Example:

Original:

      A     B     C
1    Gas    5    10
2    Air    8    12

Replace with:

     A     B        C
1   Gas    5    =15-B1
2   Air    8    =20-B2

so you only change B, and the value of C is automatically calculated.