Making Excel functions affect 'other' cells

Question

Let\'s say that I create a Sub (not a function) whose mission in life is to take the active cell (i.e. Selection) and set an adjacent cell to some value. This works fine.

Answer 1

While you can't do this in Excel, it's possible in Resolver One (although it's still a pretty odd thing to do).

It's a spreadsheet that allows you to define custom functions in Python that you can then call from a cell formula in the grid.

As an example of what you're asking, you might want to define a safeDivide function that (instead of raising a ZeroDivisionError) told you about the problem by colouring the denominator cell, and putting an error message beside it. You can define it like this:

def safeDivide(numerator, cellRange):
    if not isinstance(cellRange, CellRange):
        raise ValueError('denominator must be a cell range')
    denominator = cellRange.Value
    if denominator == 0:
        cell = cellRange.TopLeft
        cell.BackColor = Color.Red
        cell.Offset(1, 0).Value = 'Tried to divide by zero'
        return 0
    return numerator / denominator

There's an extra wrinkle: functions that get passed cells just get passed the cell value, so to work around that we insist on being passed a one-cell cellrange for the denominator.

If you're trying to do unusual things with spreadsheets which don't quite fit into Excel, or you're interested in using the power of Python to work with your spreadsheet data, it's worth having a look at Resolver One.