I've never used it, but the example in TimeConvert() appears to be close to what you want...

TimeConvert() -
http://www.kixtart.org/forums/ubbthreads.php?ubb=showflat&Number=173022

You could also just split() the time on ":" and rebuild the time in your AT. This would require some error checking but would work...

For example:
 Code:
? @time
$time=split(@time,":")
$hrs=$time[0]
$mins=$time[1]
$secs=$time[2]


? $mins