The situation was that I had a packet capture that I had used for troubleshooting an issue. The next day the question came up "hey what kind of transfer rates are we getting over this connection." I said hey i have a capture let me check and when I did using Statistics--> Summary the transmission speed that was displayed was inaccurate. That is because ethereal was determining the rate of data transfer by analyzing the amount of data transfered from the first packet to the last packet. However there was a period of significant down time between transfers that was schewing the results.
So what I wanted to do was to create a display filter so that I could get a measure of transmission speed during a set amount of time within the capture. However I was unable to figure out how and it has really bugged me because the data was there it was just a matter of filtering it out.
I may have been going about this in a inefficient manner if so let me know a better technique that the speed of transmission could be determined using ethereal. Also let me know if more clarification is needed.

Thanks!!!