I haven't done this dynamically.
Either you can estimate (back calculate) the value of a demo taking qualification rates into consideration. Obviously, this isn't very useful.
Or you can set up a conditional form with some basic qualification questions in place. Eg: for us, it's # people in the marketing team. Then only set values for the qualified conversion.
When you use either of this, consider only using funnel metrics for that channel instead of blended numbers because it may differ a lot from channel to channel.
It becomes more useful if you're also making other changes across the funnel so that things like conversion rates are also increasing so you can update this. Even though the change gets applied after a while, it's still helpful