sql insert into and update a numeric field (TotalAmount) in the dBase with value of Function (@Total)

There is an error on field {@Total}
Is there a conversion needed ?

Code:
dim iFactnr   as global
dim iDetailID as global
dim Update
 
if {?StatusFactuur} = '1'  then
       let Update  = SQL("Insert into [dbo].[Facturen] ([FactuurNr], [Date], [TotalAmount])  Values ('" + CStr(iFactnr) + "' , '" + CStr({?dsFactDate}) + "' , '" + CStr({@Total}) + "')")
end
 
return CInt(iFactnr)