• Sought advice from colleague.

    This worked (double quotes encasing a space)

    [Copy of Obj Acct] == " " ? [Copy of Sub] : ([Copy of Sub] == " " ? [Copy of Obj Acct] : [Copy of Obj Acct] + "." + [Copy of Sub])

    This didn't (double quotes encasing no space)

    [Copy of Obj Acct] == "" ? [Copy of Sub] : ([Copy of Sub] == "" ? [Copy of Obj Acct] : [Copy of Obj Acct] + "." + [Copy of Sub])

    Now the concatenation is working as intended, with no period if either [Sub] or [Obj Acct] column is empty.

    --I will need to evaluate why the excel column [Sub], when containing nothing is importing to SSIS as a space....