Hi,

Might be this would work.

sub TransformFileName($)
{
 my $FileName=shift;
 my $IdExp1=$FileName;
 my $IdExp2=$FileName;
 my $IdExp3=$FileName;

 $IdExp1=~s/(\d\d\d)(.*)?/$1/;
 $IdExp2=~s/(\d\d\d)(\d\d\d\d\d\d)(.*)?/$2/;
 $IdExp3=~s/(\d\d\d)(\d\d\d\d\d\d)(\d\d)/$3/;
 
 my @Transform=split(//,$IdExp2);
 my $value=0;
 for(my $i=0;$i<@Transform;$i++)
 {
   $value+=$Transform[$i];
 }

 my @Nsize=split(//,$value);
 my $Nzero=5;
 $IdExp2=$value; 
 for (my $i=0;$i<$Nzero-@Nsize;$++)
 {
   $IdExp2='0'.$IdExp2;
 }
 
 my $TransformedFileName=$IdExp1.$IdExp2.$idExp3;
 return $TransformedFileName;
}
[download]

I have not tested it.
I hope this is what you need.