Binary Search

Also known as half-interval search, logarithmic search, or binary chop.
A binary search is a search algorithm that can find the position of a value within a sorted array.
The function does not return the position, it just returns whether a match was found or not.
Your array must be sorted in Ascending Order for this function to work.

Public Sub BinarySearch() 
    
Dim myArray(0 To 3) As String 
Dim bfoundMatch As String 

    myArray(0) = "four" 
    myArray(1) = "one" 
    myArray(2) = "three" 
    myArray(3) = "two" 

    bfoundMatch = Array_Find(myArray, "three") 
    Debug.Print bfoundMatch 
End Sub 

Public Function Array_Find(ByRef theArray() As String, _ 
                           ByVal target As String) _ 
                           As Boolean 

Dim bfind As Boolean 
Dim low As Integer 
Dim high As Integer 
Dim middle As Integer 
    
    low = 0 
    high = UBound(theArray) 

    bfind = False 
    Do While low <= high 
        middle = (low + high) / 2 

        If target = theArray(middle) Then 
            bfind = True 
            Exit Do 

        ElseIf target < theArray(middle) Then 
            high = (middle - 1) 
        Else 
            low = (middle + 1) 
        End If 
    Loop 
    
    Array_Find = bfind 
End Function