Updating A Column In A CommonTable Expression

I'm new to CTE and I'm trying to update some columns in my cte listed below


USE ELU;

GO

WITH FollowupGrid (TransactionID,

DetailLineNum,

TransactionDate,

Quantity,

ItemDescription,

ProductSize,

TransactionType,

FollowupResolve,

ReplenishResolve) AS

(

SELECT TransactionID,

DetailLineNum,

TransactionDate,

Quantity,

ItemDescription,

ProductSize,

TransactionType,

FollowupResolve,

ReplenishResolve

FROM vwFollowupTransactions

WHERE CustomerNum = N'6299'

UNION

SELECT

r.TransactionID,

r.DetailLineNum,

r.TransactionDate,

r.Quantity,

r.ItemDescription,

r.ProductSize,

r.TransactionType,

r.FollowupResolve,

r.ReplenishResolve

FROM vwReplenishTransactions r

WHERE CustomerNum = N'6299'

)



UPDATE FollowupGrid

SET FollowupResolve = N'Yes'

FROM vwFollowupTransactions f INNER JOIN

FollowupGrid ON f.DetailLineNum = FollowupGrid.DetailLineNum AND

f.TransactionID = FollowupGrid.TransactionID

WHERE (f.FollowupResolve is null)

UPDATE FollowupGrid

SET ReplenishResolve = N'Yes'

FROM vwReplenishTransactions t INNER JOIN

FollowupGrid ON t.DetailLineNum = FollowupGrid.DetailLineNum AND

t.TransactionID = FollowupGrid.TransactionID

WHERE (f.ReplenishResolve is null)

(

select * from FollowupGrid

)

GO


When I run this query I get an error message which states"

"Update or insert of view or function 'FollowupGrid' failed because it contains a derived or constant field."

How would I go about updating the FollowupResolve and ReplenishResolve fields in a CTE?