You want the button to do the following:
Press 1: Select Source 1
Press 2: Select Source 2
Press 3: Select Source 3
Press 4: Select Source 4
Press 5: Select Source 5
Press 1: Select Source 1
Press 2: Select Source 2
etc.

So simple to do in Crestron with a Ring counter if it was discrete codes for each.
But reading your question it seems you just want to do the same function as the Source button on the remote (Single button that scrolls through sources) so just learn the code and assign to a button.