One way to do it: import all the text strings into Excel, and use the
Text to Columns feature to separate each value into a separate column.
Then delete all the alpha characters: search for G, for instance, and
replace with "" which will leave only numeric characters- then you can
do the required math on them. For clarity, insert a row to contain
headers, such as G, X, Y, Z, etc.

When that's done, use columns off to the right to calculate the
converted values. Then use a CONCATENATE function to tie it all back
together: =CONCATENATE("G", a5, " ", "G", b5, " ","X",c5, " ", "Y",
d5, " ", .....etc)

Save the Excel file as a text file and the concatenated fields will be
the text string you need.

Dave O
Eschew obfuscation