SQL Query in Excel gives "undefined function name" error - sql

Question

I wrote a SQL query in MS Access that uses the MonthName function. In access it works flawlessly. I copied the exact SQL statement into an excel module that I frequently use to query databases. When I run the query, excel keeps telling me that MonthName is an undefined function name. If I remove the MonthName portion, the query runs fine.
It seems like I'm missing a reference or something... Right now, I'm referencing Microsoft ActiveX Data Objects Library 6.0. Can anyone point me in the right direction? Thanks
strSQL = "SELECT DISTINCT Customers.CustomerName, Employees.EmployeeName, [Policy data revised].EXDT, MonthName(Month([EXDT])) AS expMonth
FROM (([Service Team table]
INNER JOIN Customers
ON [Service Team table].CustID = Customers.CustID)
INNER JOIN Employees
ON [Service Team table].EmployeeID = Employees.EmployeeID)
INNER JOIN [Policy data revised]
ON Customers.CustID = [Policy data revised].CustID
WHERE ((([Service Team table].RoleExtension)='2. Underwriting Assistant')
AND (([Policy data revised].EXDT)
BETWEEN #" & minExpDt & "# AND #" & maxExpDt & "#))
ORDER BY [Policy data revised].EXDT ASC;"

Answer 1

The MonthName() function is only available for queries run within an Access application session. See the "The following VBA functions won't work when called from a property sheet or used in an SQL statement" bullet point at About Microsoft Jet Expression Service sandbox mode. Within an Access application session, the db engine can use the expression service to use that sandboxed function.
Since you can't use MonthName, try this Format expression instead.
Format([EXDT], 'mmmm') AS expMonth

Answer 2

Strange, I just tried the following code in Excel 2010 (64-bit) and it worked for me:
Sub foo()
'' Reference: "Microsoft ActiveX Data Objects 6.0 Library"
Dim con As ADODB.Connection, rst As ADODB.Recordset
Set con = New ADODB.Connection
con.Open "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Users\Gord\Desktop\Database1.accdb;"
Set rst = New ADODB.Recordset
rst.Open "SELECT MonthName(Month([BookingStart])) FROM Payment_tbl", con, adOpenStatic, adLockOptimistic
Debug.Print rst(0).Value
rst.Close
Set rst = Nothing
con.Close
Set con = Nothing
End Sub
Edit
Further to HansUp's comment, something must have changed between Office 2007 and Office 2010. I ran another test from a 32-bit machine running Office 2010 and the above code run against an Access 2000 .mdb file worked for me using both...
Provider=Microsoft.ACE.OLEDB.12.0;
...and...
Provider=Microsoft.Jet.OLEDB.4.0;
I also checked the SandBoxMode registry value under...
HKLM\Software\Microsoft\Office\14.0\Access Connectivity Engine\Engines
...and it is 3, which is the value for "Enabled" (ref: here).