[Erel]

        Do Until r = EOF
            sum = sum + 1
            r = FileRead (c1)
            'r = StrToUpper(r)
            ChanPos = StrIndexOf  (r , "Chan := ",0)
            If ChanPos > 0 Then
                ChanText = SubString (r,ChanPos + 8, 2)
                textbox1.Text=SubString(RemoveSpaces(r),0,11)
                If SubString(RemoveSpaces(r),0,11) = "My_RetValue" Then
                    r = FileRead(c1)
                    Table1.AddRow (ChanText,r)
                End If                    
            End If
        Loop

EOF is a string mark. If you change 'r' with StrToUpper, r will never be equal to EOF.