I am looking for a way to have an error % formula change based on an selection from a drop down menu. I found the =IF function and tried writing it based on examples found but I can't get it working. Basically, if the output unit is mA, then I need an error % based on a range of 4 - 20, otherwise my range is the user entered range at the top of the sheet (this is all highlighted in red text on the file provided). I'm sure this is a basic problem but I'm just starting to use excel. Any input is appreciated.