Here is my simple recorded MSWord VBA mailmerge code. In particular, note this syntax:
[VBA]ActiveDocument.MailMerge.DataSource.QueryString = _
"SELECT * FROM `Employees` WHERE `EmployeeID` = 3" & ""[/VBA]

[VBA]Sub Macro4()
'
' Macro4 Macro
'
'
ActiveDocument.MailMerge.MainDocumentType = wdFormLetters
ActiveDocument.MailMerge.EditMainDocument
ActiveDocument.MailMerge.OpenDataSource Name:= _
"C:\MyFiles\Access\Nwind.mdb", ConfirmConversions:=False, ReadOnly:=False _
, LinkToSource:=True, AddToRecentFiles:=False, PasswordDocument:="", _
PasswordTemplate:="", WritePasswordDocument:="", WritePasswordTemplate:= _
"", Revert:=False, Format:=wdOpenFormatAuto, Connection:= _
"Provider=Microsoft.ACE.OLEDB.12.0;User ID=Admin;Data Source=C:\MyFiles\Access\Nwind.mdb;Mode=Read;Extended Properties="""";Jet OLEDB:System database="""";Jet OLEDB:Registry Path="""";Jet OLEDB:Engine Type=4;Jet OLEDBatabase Locking Mode=0;Jet OLEDB:Global Par" _
, SQLStatement:="SELECT * FROM `Employees`", SQLStatement1:="", SubType:= _
wdMergeSubTypeAccess
ActiveDocument.MailMerge.EditMainDocument
ActiveDocument.MailMerge.Fields.Add Range:=Selection.Range, Name:= _
"EmployeeID"
Selection.TypeParagraph
ActiveDocument.MailMerge.Fields.Add Range:=Selection.Range, Name:= _
"LastName"
Selection.TypeParagraph
ActiveDocument.MailMerge.Fields.Add Range:=Selection.Range, Name:= _
"FirstName"
ChangeFileOpenDirectory "X:\MSWord\MailMerge\KenExample\"
ActiveDocument.SaveAs2 FileName:="KenExample.docx", FileFormat:= _
wdFormatXMLDocument, LockComments:=False, Password:="", AddToRecentFiles _
:=True, WritePassword:="", ReadOnlyRecommended:=False, EmbedTrueTypeFonts _
:=False, SaveNativePictureFormat:=False, SaveFormsData:=False, _
SaveAsAOCELetter:=False, CompatibilityMode:=14
ActiveDocument.MailMerge.DataSource.QueryString = _
"SELECT * FROM `Employees` WHERE `EmployeeID` = 3" & ""
ActiveDocument.Save
ActiveDocument.MailMerge.DataSource.QueryString = _
"SELECT * FROM `Employees` WHERE `EmployeeID` = 3" & ""
With ActiveDocument.MailMerge
.Destination = wdSendToNewDocument
.MailAsAttachment = False
.MailAddressFieldName = ""
.MailSubject = ""
.SuppressBlankLines = True
With .DataSource
.FirstRecord = wdDefaultFirstRecord
.LastRecord = wdDefaultLastRecord
End With
.Execute Pause:=True
End With
ActiveDocument.SaveAs2 FileName:="1.docx", FileFormat:=wdFormatXMLDocument _
, LockComments:=False, Password:="", AddToRecentFiles:=True, _
WritePassword:="", ReadOnlyRecommended:=False, EmbedTrueTypeFonts:=False, _
SaveNativePictureFormat:=False, SaveFormsData:=False, SaveAsAOCELetter:= _
False, CompatibilityMode:=14
ActiveWindow.Close
ActiveWindow.Close
Application.Quit
End Sub
[/VBA]