You can convert the case of text in Excel using the UPPER, LOWER, or PROPER functions. For example, to convert a column of text to all uppercase, you would use the following formula:

=UPPER(A1)

To convert a column of text to all lowercase, you would use the following formula:

=LOWER(A1)

To convert a column of text to proper case (i.e. the first letter of each word is uppercase), you would use the following formula:

=PROPER(A1)