I am trying to establish a home gym in my backyard pergola. However it curently has screens, which do not stop dust and water coming in and also block light from coming in. I wanted to install something which can run on tracks from top and be closed/open as needed. Height is about 2.34 Metres. Width between poles behing equipment is 4.3m. Width between poles towards lawn is 2.65, 3.6 and 3.6 metres.
Am trying to understand what options are available and rough estimates of cost(probably a premature question, so apologies if it's too much of wild guess at this stage).
Welcome to the Bunnings Workshop community. It's a pleasure to have you join us, and thank you for sharing your question about enclosing your pergola.
I'm afraid the only way to properly enclose the area in order to prevent rain, dust and light from entering is to create a timber wall. Using a sliding partition will only prevent rain and light from entering, but dust will still enter from above and below the door. Since the gap is very big and the panel very tall it will need to be divided into two. The gaps created by such a structure will still let dust into your gym.
A compromise to building a timber wall is to use Bistro Blinds 0.75mm 270 x 240cm PVC Outdoor Blinds. This blind is made of PVC and will prevent wind and rain from passing through. However, it will still let dust and light enter the area. The blinds can be interconnected to one another so that you can enclose the entire area.
I suggest having a look at this discussion - How to enclose a carport? by @azza0712. Although the subject is a carport the recommendations and suggestions are all applicable to your project.