If you use Excel's IF function to compare two cells that contain text, Excel, by default, ignores the case of the text being compared. For instance, if cell B3 contains "Case" and cell B4 contains "case", then the following formula returns "Match".

=IF(B3=B4,"Match","No Match")

There is no way to modify this behavior using any settings in Excel. If you do not get these results, it is likely because of some other reason. For example, the text in the cells may look the same, but it may not really be the same. For instance, one cell could contain "Case " (with the trailing space), and the other contain "case". In this instance, the formula would return "No Match", and you would assume it is because of the capitalized C in one of the cells, but the real reason is because of the trailing space. You can confirm this by changing the formula, as follows:

=IF(TRIM(B3)=TRIM(B4),"Match","No Match")

The only difference here, of course, is that the TRIM function is used to return a cell value that has all leading and trailing spaces removed.

If you want Excel to actually take text case into account, you should use the EXACT statement, as shown here:

=IF(EXACT(B3,B4),"Match","No Match")

The EXACT function returns True if the cells are exactly the same, otherwise it returns False.