Create floors by room with Dynamo

I’m creating a routine to automatically insert floors into the model. I have already managed to insert floors in all rooms on the same level, but I need to insert the floors only in the selected rooms. How do I do that? Below is a screenshot of how far I managed to get. The “select room element” node allows me to select just one room at a time, but I need one that allows me to select multiple rooms at once. Please, can you help me? *I’m a beginner and I know this is a basic question.

You can use a custom node for multi-selection but you might be better off using a list selection UI from Data-Shapes. This would allow you to list all rooms in the model and select the ones you want by name. Either way, I’d focus on a custom UI node.