Ctrl + ` (Hint: Look for the tilde “~” symbol)
This keyboard shortcut reveals all the formulas on a worksheet. Changing cells before you know what they do is always risky. If after you reveal all your formulas, you then format those cells with a certain highlight color, when you turn the reveal feature off (just Ctrl+`, again), you will have then marked the mine field.
Find Named Ranges
Another thing to do before you start deleting worksheets you think you don’t need is to visit each worksheet that has a named range. Named ranges are used for different purposes, several of those are in formulas. Delete a worksheet with a named range, and you may be killing formulas all over your workbook! Click the dropdown arrow in the name box and select each named range. Right click on the worksheet tab and change the tab color to something like red (think: hot, don’t touch).
Use Find > Options >Find All
Expand the capabilities of FIND by choosing the Options button. In this way, you can search for named ranges or worksheet names in all formulas in the whole workbook. If you want to change something, at least you’ll know the impact!
You may find opportunities to optimize and economize, but first you have to understand with what you are starting. Using these techniques will save you hours of frustration as you take over work which others have done.