I don't know if these will do exactly what you're looking for, but they might be worth giving a go (all freeware)
The most complete, efficient and convenient freeware subtitle editing tool. It supports all the subtitle formats you need and has all the features you would want from a subtitle editing program.
Set delay (positive or negative, time or frames).
Set duration limits (maximum duration and minimum duration).
Adjust subtitles using four possible methods: 1- first and last dialogs, 2- synchronize using two points (linear algorithm), 3- Adjust to synchronized subtitles and 4- Advanced system to synchronize subtitles using an indefinite number of points.
"Time expander/reducer" to expand/reduce the final time of certain subtitles under certain conditions.
"Automatic durations" to calculate the duration of subtitles using a simple formula.
FPS Conversion with one click.
"Extend length" to extend the length of selected subtitles to the start time of the next one.
"Shift subtitle" forward or backwards a configurable amount of time.
"Read times from file" feature, to fix a subtitle using another subtitle's times.
If you like to play movies with subtitles then this is the player for you. SubEdit Player is a very easy-to-use, versatile movie player and subtitles editor. It can handle almost all common audio/video formats (with the right codecs installed) and subtitles.
SubRip is a program which allows you to rip DVD subtitles with their timing as a text file. Can also convert vobsub(sub and idx) to srt text subtitles(vobsub to srt / sub to srt).
MV2Player is freeware multimedia player for Windows, with tons of useful features... including intelligent subtitles detecting/loading