sorting data in crystal report that contains a combination of strings and numbers -

i have read how sort data in crystal report, have different issue, data want sort contain description(string) , numbers, , want sorting according these numbers ascending.. data description of stock item plus weight in kg, sorting according weight.. data like:

• boxes / kg +300 kg
• boxes / kg +1000 kg
• boxes / kg +500 kg
• boxes / kg +25 kg

they must :

• boxes / kg +25 kg
• boxes / kg +300 kg
• boxes / kg +500 kg
• boxes / kg +1000 kg

so how sort them?

create formula below:

@splitstring  stringvar s1;  stringvar s2;  numbervar n1;  s1 := {stringformat_.stringvalue}[13 20];  s2 := s1[1 length(s1)-2];  n1 :=tonumber(s2);  

place formula in report apply short on formula. after can suppress if required...