Call IndexOf to obtain the position of the first occurrence of a string that matches S. The string must be an exact match (S can't be the prefix of a string in the combo box). 

IndexOf returns the 0-based index of the string. Thus, if S matches the first string in the list, IndexOf returns 0, if S is the second string, IndexOf returns 1, and so on. If the string does not have a match in the string list, IndexOf returns -1. 

IndexOfName 

IndexOfObject 

Strings