=DSum("[Amount6a6fs]","[Sales Analysis]","[Posting Date Period] = '" &
[cbMonth] & "' And [Revenue Stream Division] = 'Production' or [Revenue
Stream Division] = 'other' And ([Customer No] = 'C01317')")

every works apart from the last par customer no, the table name is correct
spelling,
the sun i'm getting is for everything not that specifc customer.