Error checking can be performed in two different places:
1. If it happens within the panel using VER statement in the PROC section of the panel definition, then you have to do nearly nothing. ISPF controls the cursor position. The first field check which does not passed the VER statement causes ISPF to perform all statements defined in the REINIT section (if present), refreshs the panel, and positions the cursor on the corresponding field. Control is not passed back to the program.
2. If error checking is performed in your program after displaying the panel, you have to re-display the panel using the additional parameter CURSOR(field).