define temp-table tt 
  field cc1 as char
  .

def var hb as handle.

hb = temp-table tt:default-buffer-handle.

/* this should be sufficient, but when buffer-field does not exist, error 7351 is thrown */

assign 
  hb::cc1 = "one" when valid-handle( hb:buffer-field( "cc1" ) )
  hb::cc2 = "two" when valid-handle( hb:buffer-field( "cc2" ) )
  .  

/* ... so clunky code required */

def var lok as logical.

{&_proparse_ prolint-nowarn(avoidnoerror)}
lok = valid-handle( hb:buffer-field( "cc1" ) ) no-error.
if lok then 
  hb::cc1 = "one".
{&_proparse_ prolint-nowarn(avoidnoerror)}
lok = valid-handle( hb:buffer-field( "cc2" ) ) no-error.
if lok then 
  hb::cc2 = "two".