add_number_to_multiselects.py

import sublime, sublime_plugin, string

class MultiSelectNumbersCommand(sublime_plugin.TextCommand):
  def run(self, edit):
    window = self.view.window()

    def countThoseSelections(pattern):
      pattern = string.split( pattern, ':' )
      region_index = int( pattern[0] )

      for region in self.view.sel():

        replaceRegion = sublime.Region( region.begin() - 1, region.begin() )
        prevChar = self.view.substr( replaceRegion )

        if( prevChar == '#' ):
          self.view.replace( edit, replaceRegion, str( region_index ) )
          region_index = region_index + int( pattern[1] )

    window.show_input_panel('Count Start:Step (optional; default is 1:1)', '1:1', countThoseSelections, None, None)