find last alphanumeric row of .txt file and fill into excel cell

[nalsur88]

hello to all, I'm new in this forums

currently we enter manually the serial numbers and always double the number and very hard to find in list,
my idea is, create 1 button "NEW" and 1 for "SAVE" , and csv (serial_number.csv) file have serial# for beginning start with TTR000001, user press button "NEW" then create new number and place in cell B1 according to last serial number in csv file, SAVE button is save new serial number to csv file below last numbers.

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thanks hope someone to help with vba macro

the serial_number.csv file
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