Difference Between 2 Timestampl's

Hi experts,

I have 2 timestamps in String form 'YYYYMMDDhhmmssmmmuuun'. I need to find the difference between these 2 timestamps. I don't know if I need to convert the strings to timestampl's then find the difference or if there is a function module that can do that for me. Any help with this is much appreciated.

Thanks,

Bradley