I'm trying to require a value to be populated in column A if column D has an amount in it. Column A can hold any type of value (text or numerical), column D can only be a number.
So, for example, if cell D1 is 11, cell A1 would require a value, and ideally have a popup message alerting the user to the problem.
I've looked into the Data Validation function, but it seems to only validate a cell based on that cell's value. If it's possible, I haven't been able to figure out how to make Data Validation validate one cell based on the value of another.
Any ideas?
Editing to add - I'm trying to do this because I have a column of dollar amounts (column D). Column A should be the invoice number associated with the dollar amount in Column D. Each amount in column D must have an invoice number in column A. I already have conditional formatting in the spreadsheet, and apparently bright red cell coloring isn't a good enough indicator of "you did something wrong" for the individuals filling out the spreadsheet.