Need help amending macro to use one Internet Explorer Window - excel

Question

The below function opens Oanda.com and takes the currency conversion rate between USD and a input (another currency). The equation will be filled down with another macro to span 48 rows. The macro as it stands, will open 48 Internet Explorer Windows and close them after extracting the data point (1 at a time as the equation updates down the column). This process is tedious and the below method seems to be more efficient on every front but I cannot figure out how to implement:
Is there a way to amend this to first check for existing Internet Explorer window, If one is open, simply use that window to go to the domain (which is variable here) and extract data. If a window is not open, then open one. I do not know procedures to search for programs running in the background.
The main goal is to speed up the equation when it is executed by fill down. Any suggestions welcome.
Clarity Edit: I created the UDF to help me build a table. Currency tickers (USD, EUR, GBP, etc) will span Column A down to row 48. Column B needs to show the corresponding conversion rate matched against 1 USD (down to row 48). The UDF below does as intended but i'm seeking an alternative, more efficient, way to do this.
Option Explicit
Public Function ConvertUSD(ConvertWhat As String) As Double
'References
' Microsoft XML, vs.0
' Microsoft Internet Controls
' Microsoft HTML Object Library.
Dim IE As New InternetExplorer
'IE.Visible = True
IE.Navigate "https://www.oanda.com/currency/converter?quote_currency=USD&base_currency=" & ConvertWhat
Do
DoEvents
Loop Until IE.ReadyState = ReadyState_Complete
Dim Doc As HTMLDocument
Set Doc = IE.Document
Dim Ans As String
Ans = Trim(Doc.getElementsByTagName("tbody")(2).innerText)
Dim AnsExtract As Variant
AnsExtract = Split(Ans, " ")
ConvertUSD = AnsExtract(4)
IE.Quit
End Function

Answer 1

Try this:
Sub MainSub()
Dim IE As InternetExplorer
Set IE = New InternetExplorer
'
Dim x As Long
Dim Currencies As Variant
Currencies = Array("GBP", "EUR", "JPY", "HKD")
'
For x = LBound(Currencies) To UBound(Currencies)
Debug.Print "1 USD = " & ConvertUSD(Currencies(x), IE) & " " & Currencies(x)
Next x
IE.Quit ' Quit here instead
Set IE = Nothing
End Sub
Public Function ConvertUSD(ByVal ConvertWhat As String, IE As InternetExplorer) As Double
'References
' Microsoft XML, vs.0
' Microsoft Internet Controls
' Microsoft HTML Object Library.
' Dim IE As New InternetExplorer ' Commented out here
IE.Navigate "https://www.oanda.com/currency/converter?quote_currency=USD&base_currency=" & ConvertWhat
Do
DoEvents
Loop Until IE.ReadyState = ReadyState_Complete
Dim Doc As HTMLDocument
Set Doc = IE.Document
Dim Ans As String
Ans = Trim(Doc.getElementsByTagName("tbody")(2).innerText)
Dim AnsExtract As Variant
AnsExtract = Split(Ans, " ")
ConvertUSD = AnsExtract(4)
' IE.Quit ' Don't quit here
End Function
Your problem is that you keep opening a new IE every time the function is called. However if you open one before calling the function, you'll be able to re-use it as needed - and only quit after you've finished.