Possible causes and solutions
Change the formulas, or restore the cells on the worksheet by clicking Undo immediately after you delete or paste the cells.
Using a link to a program that is not running
Start the program.
Linking to a Dynamic Data Exchange (DDE) topic such as "system" that is not available
Make sure that you're using the correct DDE topic.
Running a macro that enters a function that returns #REF!
Check the function to see if an argument refers to a cell or range of cells that is not valid. For example, if the macro enters a function that refers to a cell above the function, and the cell that contains the function is in row 1, the function will return #REF! because there are no cells above row 1.