Regarding Random Generator

Question

HI all

 

I Need to Generate String Like tHIs

 

When 1st User Enter their details like 

 

FirstName 

LastName

SurName

CARDNO 

 

Automatically generate the string in CARDNO textbox

 

The string-based on Surname 

 

My Surname is: MAHESH

 

the String must be like this  AAAAM0001K

 

First 4 letters in this Sequence: AAAA

                                                   AAAB.............ZZZZ and repeat again 

5th Letter based on Surname 

 

next 4 numbers in this sequence: 0000,0001,0002.......9999 and Repeat again 

 

10th Letter must be  random a-z

 

String Must be 10 characters

 

Can any one help this 

Thanks