Calculating depths from string file

Hello,

Just wondering if someone is able to help with the question below.

I've created a DHDB and saved this as a string file to make editing of the drill holes easier. Now that I've edited the file, I'm trying to calculate the total m's for the drill program. Normally I'd export the input file data and calculate, however, since the DHDB has been converted to a string file the trace depths no longer display in the input file (I've taken a screen shot of the data headings from the string file below). Wondering if anyone knows how I might be able to get the overall m's from the string file? Thanks