KFF value set dynamically change in oracle forms

I have a KFF which has segment4 and value set xx_account.  This KFF is referred in Oracle Forms. I want this KFF segment4 to refer different value set and which should be XX_ACCOUNT_NEW.

KFF definition in form is  

FND_KEY_FLEX.DEFINE( 

            BLOCK => 'MISC_TRX', 

            FIELD => 'DIST_ACCT', 

            CODE => 'GL#', 

APPL_SHORT_NAME =>'SQLGL', 

            NUM => ':parameter.CHART_OF_ACCOUNTS_ID', 

            ID => 'dist_acct_id', 

            VRULE => '\\nSUMMARY_FLAG\\nI\\nAPPL=SQLGL;NAME=GL_NO_PARENT_SEGMENT_ALLOWED\\nN\\0GL_GLOBAL\\nDETAIL_POSTING_ALLOWED\\nE\\nAPPL=INV;NAME=INV_VRULE_POSTING\\nN',

  REQUIRED => 'N', 

VALIDATE => 'FULL',