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 ...