Change a specific character in a cell

As the topic states, I am looking to change a specific character in a cell using VBA code. The twist is how to change the character one at a time.
For example: Changing 3's to 8's one at a time for a cell, where I would want to return something like change3once = 28253.213, change3twice = 28258.213, etc

I have been searching online, but had been unsuccessful in finding a solution, and was hoping someone on here may have a good solution