Excel Macro for Number Value Modification

I need a macro script for Microsoft Excel that can change the value of a number. For example, "8,15,25,35,65,78,79" will now be "1,2,3,4,5,6,7" and the same option when i type in "1,2,3,4,5,6,7" it will convert it back to "8,15,25,35,65,78,79". There will be no preset values, so i need a way to assign a new value to each number. The output needs to be in ascending order with commas and no spaces.

So two text fields, one going each way and an easy way to assign a different value to each number.