Changing object state in a specific sequence by dropping random objects onto it

Hi,

Hopefully my title lends to the query that follows...

I have an object that I want its state to change in a sequence (e.g. 1, 2, 3...etc) when other objects are dropped onto it. These objects are the same. To clarify...

1. Object to be dropped onto is a house
   Objects to drop onto the house are plants
2. All plants are the same (so they can be dropped onto house in any order)
3. For every random plant that is dropped onto the house, the state of the house changes to show how many plants have been dropped (e.g. 1, 2, 3...)

Because the plants are the same and randomly selected by the learner to drop on the house, this is where I'm stumped for how to build this.

The final part to this is that as each plant is dropped onto the house, a layer needs to appear with a text explanation of the consequences that result from the addition of each plant.

Hope that's clear and thanks in advance for any guidance. Using Storyline 3 btw.

Andrew