There is a VirtualDub filter called subtitler.
http://www.thedeemon.com/VirtualDubFilters/detailed.html#4This plugin only supports subtitles in SubStation Alpha .ssa format and not SubRip .srt files.
You'll have to convert the .srt files to .ssa format.
Download SubMagic
http://www.submagic.tk/ to convert the subtitles.
In SubMagic, go to "File Operations" tab and open the .srt file and the save. In save dialog, select "Save as type:" as SubStation Alpha files.
Looks like there's a bug in this program. When you chose other sub formats, you must manually rename the extension from .srt to .ssa in the file name field. If you don't change the .srt to .ssa, it will save to .srt format regardless of chosen type.
Just load the .ssa file in the subtitle plugin and it'll work.
I tried it in VideoEnhancer and it works without any problem.
When testing I also only had .srt files and needed to convert.