You will need to convert each video time value into a numeric total seconds, and then make the comparison using a KM If Then Else action, something like this:
set time1 to [convert video time 1 to total seconds]
set time2 to [convert video time 2 to total seconds]
To convert video time to total seconds, see:
MACRO: Add or Subtract SMPTE TimeCode Strings [Example]
This macro contains a script that does the conversion from SMPTE time to total seconds (or total frames).
Questions?