Formulae required for serial number

i need ur help for formula for this problem, i have tried myself but still no success

say example, i need serial number in Column A, e.g 01, 02, 03, 04 and so on but with 2 conditions
in column B , there are fruits e.g B1 = Apple, B2= Mango, B3=Mango, B4= Apple, B5= Mango
and in Column C, there r months, e.g , C1= Jan-2013, C2= Jan-2013, C3= Jan-2013,C4 = Jan-2013, C5= Feb-2013
The result of serial number i want in Column A is A1=01, A2=02, A3=02, A4= 01, A5=03,

it means, if there is jan-2013 and irrespective of how many times apple come in jan-2013, the serial number must be always 01 and the serial number of new fruit after the first one e.g mango here must be 02, mango is also coming 2nd time in jan-2013, that's why its serial # is again 02 but if the same fruit e.g mango is coming in other month, serial must start in sequence, here mango is coming third time in Feb-2013, now its serial # is 03
hope u got my point
plz provide me the formula to solve this problem,
Thank u so much
waiting for ur respone

make a vlookup table with Apple and mango in column 1, the starting designation in column 2 then use formula =VLOOKUP(B1,$G$1:$H$2,2,0)+MONTH(C1)-1, where the vlookup is in range G1:H2.

see example
example.xlsx

Thanks Scott for ur time and effort, i appreciate it, i looked at ur example and found problem in it.
it is working fine the same way i want but only in starting as i increase fruits and months in vlookup table, the sequence is not in order the way i want. i have attached the same sheet of ur example with more fruits and months, plz have a look at it and see the problem and resolve it with due respect, Thanks

can you put what the sequence should be in column D so I can see what you want it to display? cause it looks fine to me, maybe extend the list a bit more so each fruit has at three months represented

as you said, i have attached the same example sheet with more detail and explained in it the result where it is showing wrong along with correction,
hope now u will get my point, plz have a look at it. Thanks

main point in all is that, whatever the fruit is, if the fruit is repeated in the same month, the serial must be of the same month of that particular fruit otherwise serial must be in order

sorry your method doesn't make sense to me, apple in jan is 1 but apple in feb is 6 and mar is 7 and it's based on occurance, so if apple comes before mango it would be different than if mango came before apple?

a serial number should be designed more simply, like first two digit = month, second digit = type (apple, mango...) or something

a formula might not be the best option if you have a ton of lines because the number of logic steps to get the outcome would be too great, you would need vba to check to see if there are repeats with in a month and to determine order

I hope someone can help you, i'm not smart enough, best of luck

Basically serial number depends on different fruits with different months, no prob Sir Scott, i appreciate for ur precious time and effort, at least u tried it, Thanks a lot for this,

Thanks Lemice, great, it is working perfectly fine, i really appreciate ur effort n time, thank u so much once again