Finding

There are three built-in functions you can use for finding substrings.

INSTR([start,] string1, string2 [,compare])

You can use the INSTR function to return the position of a substring within a larger string.
This function is case sensitive.
When start is left blank, 1 is used.
When the substring cannot be found, 0 is returned.

InStr("C:\Temp\","C:\") = 1 
InStr(1,"C:\Temp\","C:\") = 1 
InStr(1,"C:\Temp\","E:\") = 0 
InStr(1,"C:\Temp\","Temp") = 4 
InStr(1,"C:\Temp\","\") = 3 

INSTRREV(stringcheck, stringmatch [,start] [,compare])

You can use the INSTRREV function to return the position of a substring within a larger string.
This function is case sensitive.
When start is left blank, -1 is used (meaning the last character).
When the substring cannot be found, 0 is returned.
Although this function searches from the right hand side, it returns the number of characters from the left (same as INSTR).

InStrRev("C:\Temp\","C:\") = 1 
InStrRev("C:\Temp\","C:\",-1) = 1 
InStrRev("C:\Temp\","E:\",-1) = 0 
InStrRev("C:\Temp\","Temp",-1) = 4 
InStrRev("C:\Temp\","\",-1) = 8 

MID(string, start [,length])

You can use the MID - Function to return the text which is a substring of a larger string.
Not to be confused with the MID - Statement which replaces a specified number of characters.

Mid("C:\Temp\",1) = "C:\Temp\" 
Mid("C:\Temp\",3) = "\Temp\" 
Mid("C:\Temp\",3,1) = "\" 

Finding any occurrence

You can use the INSTR function to return the position of a substring within a larger string.
When the substring does not exist, this function will return zero.
When the substring is at the start, this function will return one.

Dim sText As String 
Dim sSubstring As String 
If (InStr(sText, sSubstring) > 0) Then 
   Debug.Print "substring appears" 
End If 

Finding the first occurrence

You can use the INSTR function to return the position of a substring within a larger string.

Dim sText As String 
sText = "The First Occurrence" 
Debug.Print InStr(sText, "e")   '= 3  

Finding the last occurrence

You can use the INSTRREV function to return the position of a substring within a larger string.

Dim sText As String 
sText = "The Last Occurrence" 
Debug.Print InStrRev(sText, "e")   '= 19