If you're trying to add a custom format in Excel and you see the message "No more custom formats can be added," it means that you've reached the limit for the number of custom formats that you can create in that workbook. Each workbook can contain a maximum of 256 custom formats.

There are a few ways to work around this limit:

• Use a different workbook. You can create up to 256 custom formats in each workbook, so if you need more than that, you can create additional workbooks.
• Modify an existing custom format. If you don't need all the formatting options in a particular custom format, you can remove some of them to make room for new ones.
• Use built-in formats. Excel includes many built-in number formats that you can use instead of creating your own custom formats. To see the built-in number formats, select the cell or range of cells that you want to format, then click Home > Number Format > More Number Formats.

If you still need more than 256 custom formats, there are a few third-party add-ins that can increase the limit. One option is Format Painter by AbleBits, which allows you to create up to 1,000 custom formats. Another option is Custom Number Formats by Office Labs, which allows you to create an unlimited number of custom formats.