InStr

This function determines the position of the first occurrence of one string within another string.

Syntax

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

Parameters

start
Optional. Numeric expression that sets the starting position for each search. If omitted, the search begins at the first character position. If start contains Null, an error occurs. The start parameter is required if compare is specified.
string1
Required. String expression being searched.
string2
Required. String expression being searched for.
compare
Optional. Numeric value that indicates the kind of comparison to use when evaluating substrings. If omitted, a binary comparison is performed. The following table shows the possible values for the compare parameter.
Constant
Value
Description
vbBinaryCompare 0 Perform a binary comparison.
vbTextCompare 1 Perform a textual comparison.
vbDatabaseCompare 2 Not supported.

Return Values

The following table shows return values for the Instr function.

If
InStr returns
string1 is zero-length 0
string1 is Null Null
string2 is zero-length Start
string2 is Null Null
string2 is not found 0
string2 is found within string1 Position at which match is found
Start > Len(string2) 0

There is an alternate form of the Instr function, InStrB, that you can use with byte data contained in a string. Instead of returning the character position of the first occurrence of one string within another, InStrB returns the byte position.