Error 91 upon repeated extraction from external link

Question

My function extracts exchange rate from an external website.

I can extract a single rate for a specific date.

I get error 91 when I have a list of different dates and I copy-paste the function to that whole list. (I tell Excel to apply this function for each specific date.)

Here's my code (the credit for xDoc object creation approach goes to AnalystCave at analystcave.com/vba-xml-working-xml-files/):

Public Function GetCurrToUZS(ByRef Curr As String, ByRef date_param As Date) As Currency        
    Dim xDoc As Object
    Dim xParent As Object
    Dim getRateChild As Object
    Dim corrDate As String

    On Error GoTo errorHandler:

    If Len(Curr) <> 3 Then
        MsgBox "Current identifier should be 3 letters in lenght", vbCritical + vbOKOnly _
            , "ERROR!"
        Exit Function
    End If
    'transforms the entered date to the required format of "YYYY-MM-DD"
    corrDate = Year(date_param) & "-" & Month(date_param) & "-" & Day(date_param)

    Set xDoc = CreateObject("MSXML2.DOMDocument")
    With xDoc
        .async = False
        .validateOnParse = False
        .Load "http://cbu.uz/ru/arkhiv-kursov-valyut/xml/" & Curr & "/" & corrDate & "/"
    End With

    'Get Document Elements
    Set xParent = xDoc.DocumentElement
    Set getRateChild = xParent.ChildNodes(0).ChildNodes(7)

    GetCurrToUZS = getRateChild.Text 'output of the function

    Set xDoc = Nothing 'terminates xDoc Object
    Exit Function

errorHandler:
    MsgBox Err.Number, vbCritical + vbOKOnly, "Critical Error!"
    Exit Function
End Function

As an example of the error, I have created this small Excel file on Dropbox (https://www.dropbox.com/s/dg2j6o4xjr9v488/FX%20Rate%20Extraction%20Error%20%28stackoverflow%29.xlsx?dl=0) with a list dates. The first one is completed using this function and should extract the rate easily without any error. Upon copy-pasting the formula to all the other dates, an error 91 will occur.

Answer 1

error 91 means an object is not set.

Your most likely bet is that xDoc cannot always be retrieved from the URL you specify. If I go to http://cbu.uz/ru/arkhiv-kursov-valyut/xml/usd/14.01.17 (3rd date in sheet), you'll get XML for 11.07.2017. In fact, if you go to http://cbu.uz/ru/arkhiv-kursov-valyut/xml you'll see that all records being offered, are for that specific date.

Put error handling around being unable to fetch xDoc and subsequently being unable to set xParent and getRateChild and it should work like a charm.