Hi Siva,
I have noticed all of your questions and have reviewed the answers that were provided to you.
Please look at Dennis comment to your question here
http://exchange.ni.com/servlet/ProcessRequest?RHIVEID=101&RPAGEID=135&HOID=5065000000080000001FF90000&UCATEGORY_0=_49_%24_6_&UCATEGORY_S=0
Let me summarize;
Your hardware can NOT do what you are asking!
The issue is that your hardware is not fast enough to keep up with your requirements!
Unless output impeadance is an issue, you could use the analog out functionality of your device to create a 0-5V output signal by construct an array of values that looks like what you need.
BUT
To get a 10Khz 50% duty cycle output signal you will need two values, (one for the high, one for the low).
Since your device can only do 10KHz, the best you can do is 5KHz.
Now re:the microsecond notch
NO GO with your hardware!
What you should do is first sit down and decide the actual duration of the notch and by what factor you would want to vary the width of the notch. This will tell you the maximum output rate.
You could also call NI sales and explain what you need to do and they will more than happy to suggest the right hardware.
As it stands "The horse you got, ain't never gonna pull that plow!"
Trying to help,
Ben