Altium repeated sheets
If i interpret you correctly you have made a design and put it into a schematic page. The design does a specific function. Now you want to add 30 of these functions and connect them together. If you find an error you would like to make changes to the design on one place and have it propagated to all 30 instances of the function. 

I think that you should start to look at these pages:


Multi-Sheet and Multi-Channel Design
Connectivity and Multi-Sheet Design, which is a subpage to the page above