You don't ask stupid questions...you're just verifying I'm following your instructions, I understand. Yep, I did use parentheses around the field and get the error. Below is the full formula I'm currently using for the totals.
WhilePrintingRecords;
shared numbervar SomeVar :=0;
If ({tblServiceOrders.RepToCredit} = [3, 280, 281])
and
not ({tblRepsfromAccount.FirstName} = ["Toshiba", "ABC"])
or
({tblRepsfromAccount.FirstName} = 'House') and isNull ({tblServiceOrders.RepToCredit})
then SomeVar := SomeVar + val({tblQuotes.TotalNetSell})