Sorry my dear friends for this late reply. I was a little bit busy with the last minute rush and could not check the forum.
Thanks to qorax, mirza897, jnathan, Temasek, thejackson, Classical_beat, Pippin, arlnr, amay, igbehinadara, idas, Munnimehek, anil04_10, Olabisi2010, Honolulu, fariza and farima. I will always remember you all for your helps and support.
Special thanks to arlnr for sharing the link. Regarding the Dhaka immigration's restriction on carrying dollar, we are just taking risk.
As per my understanding after talking to banks, the legal limit of Bangladesh on carrying Dollar is that an outgoing passenger can endorse 2,500 Traveler's Cheques on his/her passport, plus s/he can carry another 5,000 US Dollar without declaration. And thats all is allowed for one person, total 7,500 USD. There is a provision for applying to Bangladesh Bank for allowing to take more than that, but a few of similar applications were not approved in the past. I have gathered this information from an employee of Bangladesh Bank who is very close to mine and also from some other people.
Sohail Chowdhury