It's a bit hard to understand your question. Can you post the complete query?
You can try to use the computed phrase to fill your column:
For instance if your computed column is like:
SELECT (Column1 + Column2) * 3 AS Computed
FROM table
instead of using this to fill another table
UPDATE table2
SET ColumnA = Computed
FROM table2 INNER JOIN table ON table1.ID = table2.ID
WHERE ...
you can use this to fill another table:
UPDATE table2
SET ColumnA = (table2.Column1 + table2.Column2) * 3
FROM table2 INNER JOIN table ON table1.ID = table2.ID
WHERE ...