Adding numbering to seleceted cells

Hello,

I have a excel sheet where i am listing a lot of numbers, and i want to make a button that will automatticly number my selection.
but there is also another number in that cell

so if i would select A3:A10 it whould have the original number and -1 -2 etc
so this i what it should look like afther the command button is clicked:
1-1
1-2
1-3
1-4
etc

where i would have already entered the 1 in every cell.
I know how to create the buttons etc i just need help with the code.

thanx in advance

It almost works except for it only takes the numbers 1 3 5 7, this probally has to do with the i = i + 1 where it takes 1 and for the second time i + ( i + 1) but i do not know how to fix this myself