There are several ways to prevent values less than zero from displaying in Microsoft Excel. You can use conditional formatting to change the color of the cell to hide the value. Using this method retains the value in the cell so you can use it in other formulas. Alternatively, you can convert negative numbers into blank cells or dashes. Using this method does not retain the value in the cell.
Hide Negative Values With Conditional Formatting
Select the cell(s) in your Excel spreadsheet you wish to format.
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Click "Conditional Formatting" under the "Format" menu.
Select "Cell value is" from the first drop-down menu for Condition 1.
Select "less than or equal to" from the second drop-down menu.
Enter 0 in the next box.
Click on the Format button and select white in the color drop-down menu. If the background color of your cells is something other than white, select a color that will blend in and make it appear as if the cell is empty.
Click OK. Any cells you have applied this conditional formatting to will appear to be blank if the value in the cell is equal to or less than zero. If you place your cursor in the cell you will be able to see the cell's actual value in the formula bar at the top of the worksheet.
Display Negative Values As Blank Cells or Dashes
Use the IF function to specify the format of a result that is equal to or less than zero. The syntax of the IF function is IF(logical_test,value_if_true,value_if_false)
Enter 1 in cell A1 and enter 2 in cell A2 of your worksheet.
Create an IF formula in cell A3 by typing: =IF(A1-A2>0,A1-A2,"-"). In this example the logical test is whether cell A1 minus cell A2 is greater than zero. If it is the "value_if_true" it will display; if it isn't, the "value_if_false" will display. In our formula we defined the value_if_true as the difference between cells A1 and A2 and the value_if_false as a dash. Therefore, if A1-A2 is zero or less you'll see a dash in cell A3, if the result is positive, you will see a number.
Change the values in cells A1 and A2 to see how it affects what displays in cell A3.