This will give you your result list. You can then join with your limit list and apply the limit criteria:
SELECT CustomerID, Amount, SettlmtDt, DSum("[Amount]","tblInvoices","customerID='" & [customerID] & "' and [SettlmtDt] between #" & [SettlmtDt]-2 & "# AND #" & [SettlmtDt] & "#") AS Result...