VLookup / Finding Reverse Entries In Two Columns?

I have a dataset that looks like below -

Header1 Header2 Data
100 101 20.50
102 19
103 1003.2
101 100 20.50
200 300
102 100 20
200 104 30

Now, what i need to do is for each of the rows in my dataset, I need to find the reverse entries (consider first row where header 1 is 100 and header2 is 101, I need to search the entire dataset to find if I have some data for header1 is 101 and header2 is 100). In this case, I do have such data where header1 is 101 and header2 is 100.

Header1 Header2 Data Reverse Entry Difference
100 101 20.50 20.50 0
102 19 20 -1
103 1003.2 Not found Not found
101 100 20.50 20.50 0
200 300 30 270
102 100 20 19 1
200 101 30 300 -270

let me know if that's possible through excel formulas?

I need a column D with such data and column E for differences. So that, my final output should look like below -