"A" records missing for NS - suggest a sol

[SRINIVASU V V S]

hi all,
   If the NS records are present and the corresponding 'A' records are 
missing then we will start using sysquery() to resolve the address of the 
name server. but my doubt is
  if some of the name servers addresses are present and some are missing in 
the "list of name servers(SLIST)"  that we are going to query.. then what 
is the solution .. plz suggest a procedure for the above

thanks in advance,
srini