I'm not sure if this is your issue or not, but I've run into instances where I get a message that says something like "Not an updatable query". I have not been able to identify a cause and this has even happened to me after an update query has worked fine for months.
The way I get around it is to make it a two-step process. Change the update query to a make table query that dumps the output to a temporary table. Then run an update query using the temproary table instead of the SQL server table.
If you do it in a macro or code, you can then delete the temp table.
Unfortunately, I don't know anything about ASP, but I assume it will allow you to launch queries through code. You don't have to do it in a macro. I was just saying that if you did use a macro, you could add a step that would delete the temporary table when you finished.
What you can do is create one make-table query that retrieves the data you want and puts it into a table; call it tblNewData.
Then create an update- or append-query that takes the data from tblNewData and updates or appends (whichever is appropriate for your operation) the data in your existing table.
In VBA, you would write a procedure that runs the first query and then the second and then deletes the temporary table.
'Turn off "You are about to . . . " and "Do you really want to . . ." warnings
'Run query to retrieve data
'Run query to update data in your existing table
Each row is one step in the macro. In action, select what you want to do from the drop-down list and enter parameters in the fields at the bottom of the screen. (F6 switches between the upper and lower panes)
I would start with SetWarnings as my first action and enter No in the Warnings On field at the bottom. If you don't do this, you will get messages for each action query in the macro (i.e. "This query will change data in a table, do you want to continue?", "About to add x records to the table")
Next, enter the steps you want the macro to perform. To run the make table and append queries you have created, you will want to select OpenQuery in the Action field at the top and the name of the query in the Query Name field at the bottom.
Finally, enter another SetWarnings step and set it to Yes. If you don't do this, other warning/error messages (that you should want to see) will be surpressed and if you try to do something that would normally cause an error, it will seem to just ignore you and not work. (frustrating until you figure it out)