Today my wife and Children attended at Chenai consulate for H4 Visa, they are rejected. asking them 'need a letter' from me why have changed 2 companies within 16 months.

i need to write a letter to US CONSULATE in Chenai giving the reasons why I have changed 2 companies with in 16 months.

my wife and children have to attend again any Tuesday/wednesday/thursday from 9AM TO 12.00 NOON

If anyone faced such a situation , how i have to write a letter to the Officer,
if anyone has samples letters pl. send it to me
my mail Id is [email protected]