Excel Minutes seconds using Excel Custom format

[thowe]

I need to report in minutes and seconds only. The minutes can be up to 5 digits. I have tried to add a custom format: [h]mmmm:ss, [m]:ss,[mmmm]:ss. What I get when I enter the value is a date or some other value than what I entered. Example 2220:00 and 545:00. Thank you for your help