Extract specific length numbers from string and create new string with those numbers

I have a text field that I need to extract certain numbers from. The number will always be 7 digits long but the location within the string is not known and how many are in the string is also not known.

A sample string is "SF WO 1564892 DUE 5/19 FIN WO 1638964 DUE 5/27". I want to be able to extract 1564892 and 1638964 and have it generate a new string like "1564892;1638964" and continue to add ";number" if there are more in the string. I use the new string to find and return the largest of these numbers.

I found this and it kind of works but it will also return "1234567" from the string "123456789" which is undesired.

Public Function ExtractDigits(Alphanumeric As String, DigitLength As Long)
Dim StringLenght As Long
Dim CurrentCharacter As String
Dim NewString As String
Dim NumberCounter As Long
Dim TempString As String


StringLenght = Len(Alphanumeric)
For r = 1 To StringLenght
    CurrentCharacter = Mid(Alphanumeric, r, 1)
    If IsNumeric(CurrentCharacter) Then
        NumberCounter = NumberCounter + 1
        TempString = TempString & CurrentCharacter
        If NumberCounter = DigitLength Then
            If NewString = "" Then
                NewString = TempString
            Else
            NewString = NewString & ";" & TempString
            End If
        End If
    End If
    If Not IsNumeric(CurrentCharacter) Then
        NumberCounter = 0
        TempString = ""
    End If
Next

ExtractDigits = NewString

End Function

I would prefer the solution be in VBA and not a function but I am open to anything.