How to use user input value, multiply this value by 5 then stretch block that has multiple objects with new value?

[CoraForun]

This is a simple dynamic block with a stretch parameter. However, I want to make it more advanced. 
What I need:

• In the properties tab, I want the user to input a length value.
• I want the stretch parameter to use this value and multiply it by 5.
  • Exemple: User enters 2 in the properties tab. Block length is now 10m long.

Note: The insert point of the block is at 0,0 and the stretch is done going downward. So if the input value is 2, I need the block to stretchs 10m south (X: 0, Y: -10).
How can I achieve that? 

I tried using vertical constraint parameter and it partly worked, but it seems that constraints parameters only works on single objects and only lines, polylines and arcs... I have text, hatch, an attribute and a visibility state in the block.

[MMcCall402]

How about a second linear parameter and stretch action with a distance multiplier of 5.  Use the current parameter as the selection set and chain its action.  The user can set the value of this parameter in the property window and it will operate the first one by a multiplier of 5.

[CoraForun]

Hello, thanks for you reply. Would be kind of you to do a demo. Are you sure this is supposed to work? It doesn't work for me. I do a linear stretch, I select every object to be stretch and set Chain Actions to Yes, but when I test, nothing moves. 

[MMcCall402]

This what I was thinking:  The stretch on the left stretches the objects at a 1x multiplier.  The stretch on the right stretches the stretch on the left at a 5x multiplier, which then stretches the objects that same amount.  The left parameter is hidden from the user, only the one on the right is visible.

[j.palmeL29YX]

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@CoraForun wrote:

I tried using vertical constraint parameter and it partly worked, ...

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If you consider a constraint based solution (additional to Marks suggestion), please post your current not yet properly working attempt. So we can see what is going wrong. 

[CoraForun]

Thank you for your help! I tested your block but when I enter 2 in Enter_Distance, the result is 6. 

[Brock_Olly]

Because the base distance is 1. Stretch one then 1x5=5 -> add both = 6

[j.palmeL29YX]

Attached an attempt using constraints. 

The vertical dimension is for testing purposes only and should be deleted in the final version.