How to read and write data automatically to/from RTDX blocks in a gui?

I know how to read data from a to RTDX block, but I'm not sure how to write it to a from RTDX block without using a button in a gui. I have done several examples like such but usually with a button. I want this to be automatically as soon as the data gets read. Can someone help me out?

Thanks, Lina.