Bash script to build up a command

I know how to use getopts to get input to my bash script, and I know how to write a loop.

What I want to do is to prompt for a start and end points to cut from a video file, and then to build up an ffmpeg command to process the file (I know how to do that).

So it will prompt for

file name - just once - no problem here
then it should prompt for

Start

End

repeat this till it gets an E for Execute

Then I know how to write loop using a count on the number of start /end pairs read.

Quedtion how do I store the start/end pairs, in an array or a list, or some other way?

I'm just looking for some tips please.