The query does not know.  You have to modify the query programmatically to
get it included.  Here is a function that will create a string you can use to
include the selections in the query:

Private Function BuildWhereCondition(strControl As String) As String
'Set up the WhereCondition Argument for the reports
Dim varItem As Variant
Dim strWhere As String
Dim ctl As Control

   Set ctl = Me.Controls(strControl)
   
   Select Case ctl.ItemsSelected.Count
       Case 0  'Include All
           strWhere = ""
       Case 1  'Only One Selected
           strWhere = "= '" & _
               ctl.ItemData(ctl.ItemsSelected(0)) & "'"
       Case Else   'Multiple Selection
           strWhere = " IN ("
           
           With ctl
               For Each varItem In .ItemsSelected
                   strWhere = strWhere & "'" & .ItemData(varItem) & "', "
               Next varItem
           End With
           strWhere = Left(strWhere, Len(strWhere) - 2) & ")"
   End Select
   
   BuildWhereCondition = strWhere
   
End Function

You can use this to filter the report by one or more managers:

   strRptFilter = "[MANAGER] = " & BuildWhereCondition(Me.lstMgrs.Name)
   DoCmd.OpenReport "SomeReport", , , strRptFilter