' FB 1.05.0 Win64

Open "manip.csv" For Input As #1 ' existing CSV file
Open "manip2.csv" For Output As #2 ' new CSV file for writing changed data

Dim header As String
Line Input #1, header
header += ",SUM"
Print #2, header

Dim As Integer c1, c2, c3, c4, c5, sum

While Not Eof(1)
  Input #1, c1, c2, c3, c4, c5
  sum = c1 + c2 + c3 + c4 + c5
  Write #2, c1, c2, c3, c4, c5, sum
Wend

Close #1
Close #2