grouping struct array based on two different field thresholds

I have a very big struct array with some fields. I want to group it to a new struct array based on just 2 fields as below (this is just for the first group. after grouping each one the remaining stand the original struct and it iterated until grouping all of them): m=2; b(new).alfa(1)=a.alfa(1); b(new).Distance(1)=a.Distance(1); for i=1:size(a.alfa,1) if ((a.alfa(1)-a.alfa(i))<threshold1) & (a.Distance(1)-a.Distance(i))<threshold2)) b(new).alfa(m)=a.alfa(i); b(new).Distance(m)=a.Distance(i); m=m+1; end end

it is a correct way but very slow one. I wanna a very fast tricky way. Thanks in advance

[Geoff Hayes]

Sepideh - please format the code in your question so that it is readable. Highlight the code portion and press the Code {} button.