Identifying groups of lines between start and end indicators

I have a set of data which represents orders and the lines within those orders. In the attached example there are three orders. Within an order there are lines for specific materials which represent the start and end of a bundle of products (70000140 and 70000141 in the attached sample). An order may have one or more bundles. There may be lines which are not in bundles at all (i.e. not between a start line and an end line). I need to create an identifier for each bundle, and then a sequence number of each line which is within each bundle (columns E and F in the attached, created manually for this example). I feel sure this can be done using functions such as INDEX and MATCH, but I can’t work out how to do it. All help and advice would be very much appreciated.

Brilliant solution, thanks so much. (For other readers, great example of using COUNTIF and COUNTIFS)