Do you want to post your REXX code? It seems like an error within your REXX exec.
The sample code below displays three ISPF panels:
/* rexx */
panels = 'panel1 panel2 panel3'
Do i = 1 to Words(panels)
the_panel = subword(panels, i, 1)
address ISPEXEC "display panel("the_panel")"
If...