The American Optometric Association suggests that children should have their first regular eye exam at six months of age. Another vision exam should take place when a child is around two or three years of age when their vision undergoes its most rapid development and vision correction is most effective.
The ISNUMBER function is a quick, easy way to check if a cell contains a number. Our example used the IF function to illustrate how ISNUMBER can be used. If you haven't used IF in a formula before, you can read our lesson on the IF function here.
Select the cells with the formulas you want to lock. To select non-adjacent cells or ranges, select the first cell/range, press and hold Ctrl, and select other cells/ranges. To select all cells with formulas on the sheet, do the following: 1  Go to the Home tab > Editing group, click Find & Select button, and choose Go To Special. 2  In the Go To Special dialog box, check the Formulas radio button (this will select the check boxes with all formula types), and click OK: