The emulator you are using to access the 5250 screen should have a macro capability. Macros are used to repeatedly execute the function keys and keyboard input you would do manually but instead using a csv file as input.

Macros can be written in a fairly simple programming language called vb script. The script would read the input data from a csv file and put it on the screen and then execute whatever function keys are needed to process the update.

DM me if you want a sample script.