You can't do it with the hours:minutes in Excel as-is.
Judicious extracting of hours and minutes, and then pasting strings together would do it.
Here's a scruffy example that shows how.
The key bit is that the numbers are formatted as text after the initial few lines.
I've assumed your hours are at least a 4-digit number or you wouldn't be bothering.
I'm sure all that lot could be wrapped up in a single formula, but I need to get some sleep
