Use the Cell Styles
Say you wanted to use this little price sheet for data entry. You can format the Cell Styles to show which Cells are for Input and which ones are Calculated (no data entry).
2. Try it: Apply a Cell Style
Select Cells
B2 through B6.
Go to Home->Styles->Cell Styles.
Select a Style: Input.
And Try This: Apply a Different Cell Style
Select Cell B7.
Go to Home->Styles->Cell Styles.
Select a Style: Calculation.
What Do You See? The Cells are formatted differently giving your users strong visual clues.
That works.