Here mr lazy is ya alias!

Code:
;
;usage $splitup(source,destination folder/file) * Do not add .txt!
;
alias Splitup {
  if (!$isfile($1))                    { return -1 } | ; invalid source file
  if (($nofile($2)) && (!$isdir($v1))) { return -2 } | ; invalid destination folder
  if (!$mkfn($nopath($2)))             { return -3 } | ; invalid destination file
  var %i = 1 | filter -cffr 1-5000 $+(",$1,") $+(",$nofile($2),$mkfn($nopath($2)),%i,.txt")
  while ($filtered) {
    inc %i | filter -cffr $+($calc(1 + %i * 5000),-,$calc(5000 + %i * 5000)) $+(",$1,") $+(",$nofile($2),$mkfn($nopath($2)),%i,.txt")
  }
  remove $+(",$nofile($2),$mkfn($nopath($2)),%i,.txt") | dec %i
  return %i
}


//echo -a i made $splitup(C:\1Report\text.txt,otherfilename) files