My suggestion would be to read the reference from a text file in the data folder rather than from the GV. Create a text file with “text0@test.com” at the top. Read the reference from the text file, manipulate the reference, write the new reference back out to the text file. Once you have read in the reference of the text file, equate it to your GV.
The alternative is to read and write the reference to Excel. That has been discussed many times on this forum. You need to persist the reference between runs and it does not look like GV are a means to do that.
This is based on the following: