Finding code associated with a worksheet

This has probably been asked and answered before. So apologies for that, but I couldn't find it from cursory searching.

Is there a good way to find code associated with a particular workbook. I have recently inherited some worksheets and there are some macros (specifically there appears to be a macro that hides rows in a sheet depending on the contents of another cell) - There's a cell wherein you select a name from a dropdown (I believe created using the data validation tool). Column A is set to 1 if the name matches the Name column, or the selected name is All and 0 otherwise. The row (used) to be hidden if column A was 0. But I've added some columns, and now the macro doesn't behave as expected.

=IF(OR(ISBLANK($C$1),$C$1="All"),1,IF($C$1=F12,1,0))

I can't find the (I guess) VBA code that does this. Is there a list of places I should look for it. I've added developer mode to my ribbon, and had a flick through the Workbooks/Sheets etc for the routine in the Visual Basic editor.

Is there a way to interrogate a cell to find out what it's doing when it is updated?

Thanks in advance for your help
(Office Pro 2013 if it's important).