help to change code??

VB Code:

Private Sub Form_Load()
Dim blnStartReading1 As Boolean, blnStartReading2 As Boolean
Dim strTestData As String
Dim A As Integer
Dim B As Integer
Dim i As Integer
Dim ii As Integer
Dim strLatitude As String
Dim strLongitude As String
Dim strDepth As String
ChDir App.Path
 
 
'Open strfilename For Input As #2
Open "test.txt" For Input As #2
    blnStartReading1 = False: blnStartReading2 = False
    
    While Not EOF(2)
        Line Input #2, strTestData
        If strTestData = "STOP" Then blnStartReading2 = False
        
        If blnStartReading1 = True And blnStartReading2 = True Then
            A = Len(strTestData)
            For B = 1 To A
                If Mid(strTestData, B, 1) = " " Then
                    strLongitude = Mid(strTestData, 1, B - 1)
                    strLatitude = Mid(strTestData, B + 1, A)
                    Exit For
                End If
            Next B
            
        'MsgBox " " & strLatitude & " " & strLongitude & " " & strDepth & ""
        Open App.Path & "/Data.txt" For Append As #3
            Print #3, " " & strLatitude & " " & strLongitude & " " & strDepth & ""
        Close #3
 
       End If
                     
        If blnStartReading1 = True And blnStartReading2 = False Then
            i = InStr(strTestData, "174=")
            ii = InStr(i + 1, strTestData, ";")
                If i < ii And i <> 0 Then
                    strDepth = Mid(strTestData, i, ii - i)
                End If
            blnStartReading2 = True
        End If
      
      If strTestData = "EndHeader" Then blnStartReading1 = True
      If strTestData = "STOP" Then blnStartReading2 = False
      
    Wend
Close #2
End Sub

From the "text.txt" file,i only need the value inside "START 43, L, 174=0;133=300000" and "STOP" to change to the format below. By using the code above,i found mistake was happen(the blue color). i don't need to save the blue color value.
3.85663000 100.81888000 174=0
3.85625000 100.81778000 174=0
3.85519000 100.80883000 174=0
3.20013000 101.29401000 174=20
3.20232000 101.29359000 174=20
3.20748000 101.29134000 174=20
2.85667000 99.98843120 174=20
2.85667000 99.70000000 174=20
3.19926000 99.70000000 174=20
3.73802000 100.94623000 174=20
3.73897000 100.94658000 174=20
3.74430000 100.94950000 174=20
3.76365000 100.98286000 174=20

this code will open your file and read it all into memory to work on

VB Code:

Dim strfile As String, resarr() As String, i As Long, pos as long, pos1 as long
Open "test.txt" For Input As 1
    strfile = Input(LOF(1), #1) ' read whole file
    Close 1
    pos = 1
    Open "Data.txt" For Append As 1
    Do
    pos = InStr(pos + 1, strfile, "START 43, L, 174=") 'find start position
    If pos = 0 Then Exit Do ' if no start position found finish
    
    pos1 = InStr(pos + 1, strfile, vbNewLine) + 2
    resarr = Split(Mid(strfile, pos1, InStr(pos1, strfile, "STOP") - pos1 - 2), vbNewLine)
      ' split the text in the lines between start and stop into an array
    For i = 0 To UBound(resarr)  ' process each line in array
        pos1 = InStr(resarr(i), " ") + 1
        resarr(i) = Mid(resarr(i), pos1) & " " & Left(resarr(i), pos1 - 2) _ 'swap order of line
        & " " & Mid(strfile, pos + 13, InStr(pos + 14, strfile, ";") - pos - 13) ' add the 174 bit
    Next
    Print #1, Join(resarr, vbNewLine) ' print all lines in group to file
    Loop
    Close 1

thanks westconn1.

but i still got problem, because my original file hv other format like below.It is not only format in blue color

START 43, L, 174=0;133=300000
3.85663000 100.81888000
.....
STOP
START 43, L, 133=250000;174=5
......
STOP
START 43, L, 133=250000;174=50;102="Approximate depth contour"
.....
STOP
START 43, L, 174=50
......
STOP
START 43, L, 174=100;133=300000
.....
STOP

change the initial search string to find the start position so that it will work with all your strings,

i thought you only wanted to find the ones that had 174 = something so i searched upto the 174, if you want all values, just search to the "L"

if you need more help, give more examples of ones you want to include and ones you want to exclude, i only worked to the sample file you posted