I am a new user of Access. I am not sure this is a right question.
Assume I have two tabels

        Jan    Feb    Mar    Apr    May    Jun
Table 1    Budget    98    98    56    45    879    99

        Jan    Feb    Mar    Apr    May    Jun
Table2    Actual    89    89    95    54    879    89

I want to set up a query. in the query, I will use budget number only if
actual is not available, once the actual number is available, I will replace
with actuals.
For example, if January actual is available, I will replace budget(98) with
actual (89).

Query        Jan    Feb    Mar    Apr    May    Jun    Total

        Actual    Actual    Budget    Budget    Budget    Budget   
        (If avaible)    (If avaible)                   
My problem is I have to change the total operations every time when I change
the column heading of the query.

thanks for your help.