You can search a selection or a worksheet for a particular word or number by using Excel's Find and Replace feature. To use Find and Replace, click the Edit menu and select the Find option, (Edit -> Find) or use the Shift + F5 shortcut.

This will display the Find and Replace dialogue box

Type what you want to find in the text field (the drop down list contains recently used search terms that you can select from) and click the Find All button or the Find Next button. If you click the Find All button, Excel will provide a list of cell references that contain the text or number that you are looking for. Clicking Find Next will take you to the next cell found that contains the text or number you are looking for.

If you click the Options button, The dialogue box will present options for refining your search.

You can now choose to search within a sheet or workbook, or by rows or columns, by making selections in the drop down lists.

If you click on the replace tab, you will be presented with the option to enter a replacement term for the one you are finding.

If you enter a term in the Replace with field, Excel will search for the word or number entered in the Find what field, and replace it with the replacement term. All you have to do is click the Replace button each time Excel finds something.

If you click the Replace All button, Excel will replace every instance of the word or number it finds with the replacement term, without waiting for you to click Replace for each one.

You can use Find and Replace on a selection of cells as well. Just select the block of cells you want to search through, and then while the selection is still highlighted choose Edit -> Find.