Is it possible to set a default value "X" to an existing checkbox? For example we would like to set default value "X" for checkbox [RF05A-CPFKB] in transaction FBR2.
Default="X" works well for newly created checkboxes...
Thank you for your answer...

You can use a "Set" command. In order to avoid the repetition of "Set" being done each time the user performs any other action (like F1, F4) on the screen, I suggest you use the system variable V[_transactionid] in the following way:

if  not V[fbr2_transactionid=&V[_transactionid]] 

  Set C[RF05A-CPFKB]    "X"

  Set V[fbr2_transactionid]   "&V[_transactionid]"