How about something like this
[inlet~] [delread whatever] | / [+~] | [bang~] [/~ 1] [1 ] [+ 1] (the object 1 is a float with default value 1) | [tabwrite~ result] [delwrite whatever block_size_in_ms]
This is meant to be a recursive way of adding them up. You'll just have to be able to start and stop it at the right time. you might be able to use [tabplay~ result] instead of delwrite and delread good luck! Chuck