Is it possible to use EF Function Translation during an Add in Entity Framework 5?

Long story short, we have spent the past few days creating a translation to add decrypt/encrypt by key into Entity Framework.

The following select works (the hardcoded key "test" is just for a testing environment, this will be stored with keystores later) The EF.Functions.Decrypt triggers a translation expression that writes custom SQL for Entity Framework to utilize the internal decryption methods.

var filteredSet = Set.Include(x => x.Table2)
            .Where(x => x.Id == id)
            .Where(x => x.Table2.IsSomething)
            .Select(m => new Model
        {
            Id = m.Id,
            Decrypted = EF.Functions.Decrypt("test", m.Encrypted), //string
            Table2 = m.Table2,
            Encrypted = m.Encrypted //byte[]
        }).ToList();

The following (as I sort of expected going into it) does not.

public Model createNew(string Data)
    {
        Set.Add(
                new Model
                {
                    Encrypted = EF.Functions.Encrypt("test", Data)
                }
            );
        return new Model();
    }

When used in this manner it attempts to create a new model object using the EF Function and throws an InvalidOperationError. Is there a way to perform an Add in EF where it translates this function rather attempting the execute the code into a model?