I do think it would be really awesome to provide User Defined Instructions though. An instruction block that when you drag it into the ladder window a new window opens on the screen where you can choose how the instruction will be set up. Either as a custom ladder block or even C++ code like the P1AM can use. That way a user could program some custom function that may not be available with any existing instructions or possibly write a function in 1 instruction block that would take a dozen rungs to create using individual instructions. The ability to augment our ladder code with some custom C++ functions if we wanted to would be pretty nice.

When clicking to accept the instruction code it will do a test compile and execute and report an error back if it won't compile right. Then when the rung becomes active and the PLC executes the instruction it just runs the custom code written within that instruction. Place some limits on the size of the instruction and/or dependencies so people don't write entire programs in an instruction that way, only smaller more individual functions. Variables used within the code would just be the tags that are also available in the main ladder program.