Hidden Questions and Piping Based on Numeric Response in Constant Sum

Apologies about the double-barreled question, but I am struggling on a couple of things:

1) Is there a simple way to create a HIDDEN or BEHIND the Scenes question. The purpose would be to generate a text substitution, based on responses to a prior question. In the example below I would like to pipe, a text substitution in Q4 (based on the responses to Q1 and Q2)

2) How do you create display or skip logic based on a numeric response given in a Constant Sum question? In the example below, I want to be able to ask Q4 to those who used Brand 1 the most (largest percentage) at Q1.

Here is the example. Figured it is easier to show the actual questions, I am trying to work with.

Thank you, in advance!

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1. For what percent of the [INSERT Qx] xxx procedures you personally performed in 2018, did you use the following brands? Total should sum to 100%.

1 Brand 1
2 Brand 2
3 Brand 3
[CONSTANT SUM] 100%

2. For what percent of the [INSERT Qx] xxx procedures you expect to perform in 2019, will you use the following brands? Total should sum to 100%.

1 Brand 1
2 Brand 2
3 Brand 3
[CONSTANT SUM] 100%

3. [HIDDEN QUESTION: CHANGE IN BRAND USE – STORE FOR TEXT SUBSTITUTION IN Q4…]
Brand 1
1 'using fewer' (ASSIGN IF % at Q2/1<Q1/1)
2 'no longer using' (ASSIGN IF % at Q2/1=0 AND Q1/1>0)
Brand 2
3 'using fewer' (ASSIGN IF % at Q2/2<Q1/2)
4 ' no longer using' (ASSIGN IF % at Q2/2=0 AND Q1/2>0)

[IF USED BRAND 1 MOST (Largest percent at Q1) in 2018 AND ‘no longer using’ OR ‘using fewer’ BRAND 1 in 2019, ASK Q5]

4. It appears you are [INSERT TEXT FROM Q3_1] Brand 1 systems in 2019, compared to 2018. Why are you [INSERT TEXT FROM Q3_1] Brand 1)?
[TEXT BOX]