Were you wanting the HTC factors nested within the blocks?
If so, you can try something similar to: Constructing a custom design with two nested random blocking
You would then want to remove all the "false VHTC factor" terms from the model if you use RSM. I've included code below to give you an idea of the setup.
The "Whole Plots" column is your block, while Subplots for your HTC factors. You would remove the "false VHTC factor column". When modeling, you would have to consider switching the blocking factor (ie. Whole Plots) from a random effect.
Hope this helps.
Cheers,
Ryan
DOE(
Custom Design,
{Add Response( Maximize, "Y", ., ., . ),
Add Factor( Continuous, -1, 1, "false VHTC factor", 2 ),
Add Factor( Continuous, -1, 1, "X2", 1 ),
Add Factor( Continuous, -1, 1, "X3", 1 ),
Add Factor( Continuous, -1, 1, "X4", 0 ), Set Random Seed( 1390686764 ),
Number of Starts( 2000 ), Add Term( {1, 0} ), Add Term( {2, 1} ),
Add Term( {3, 1} ), Add Term( {4, 1} ), Add Term( {2, 2} ),
Add Term( {2, 1}, {3, 1} ), Add Term( {3, 2} ), Add Term( {2, 1}, {4, 1} ),
Add Term( {3, 1}, {4, 1} ), Add Term( {4, 2} ), Set N Whole Plots( 3 ),
Set N Subplots( 10 ), Set Sample Size( 30 ), Optimality Criterion( 2 )}
);
