Dim line As String = "dfg  kld  hfgk    8:4  //sfga  sgasg  "
 
Dim bl As Integer = line.IndexOf("//")
 
Dim start As Integer = bl
Dim charfound As Boolean = False
 
Do
    start -= 1
    charfound = charfound Or line(start) <> " "c
Loop While start > 0 And Not (line(start) = " "c And charfound)
 
Dim substr As String = line.Substring(start, bl - start).Trim