This test will return FALSE until the range C5:C7 contains three numbers. The logical test is based on the COUNT function, which counts numeric values: COUNT(C5:C7)=3 // returns TRUE or FALSE Translation: if the count of numbers in C5:C7 is 3, sum the range C5:C7. In the example shown, we are using the IF function together with the COUNT function: =IF(COUNT(C5:C7)=3,SUM(C5:C7),'') The best solution depends on the requirements of the project and your personal preference. Below are several examples of how you can approach this problem. The logic can be adjusted in many ways to suit the situation. You can use the same approach with any formula to prevent calculation until all required values are available. In the worksheet shown, the SUM function is used as an example only. The goal is to verify the input of all required values before calculating a result.
