String Functions

To find if a string contains another string, you can use InStr and InStrRev (InStrRev is only in VB6). These return the first and last positions of a string contained in another string, respectively. They both use the following syntax:

InStr$(Start,StringToSearch,StringToFind, SearchMode)

Start is an optional figure representing the position to start searching the string. StringToSearch contains the string that you want to search. StringToFind contains the string that you want to find. The following code gets the text from txtFindString and highlights the first occurrence of that string in txtSearchString. vbTextCompare tells the InStr function to find matching strings, regardless of case. Use vbBinaryCompare for the search to be case sensitive.

Sub Command1_Click()
    ' Get the first occurrence of the string
    StringPos = InStr(1, txtSearchString, txtFindString, vbTextCompare)
    If StringPos = 0 Then
        ' If StringPos returns 0, then the string is not found
        Msgbox "String not found"
    Else
        ' Get the length of the string to find
        StringLen = Len(txtFindString)
        ' Set the starting position of the selection
        txtSearchString.SelStart = StringPos
        ' Set the selection length
        txtSearchString.SelLength = StringLength
    End If
End Sub

You could change InStr to InStrRev to find the last occurrence of the Find String.