Convert a semi-trasparent png image to a semi-transparent mbm image

I want to create an operator logo of my name on my Nokia C5-00.2.
But, as you know that Symbian Phones only support MBM images as an operator logo.
Now, My Problem is that I've a Created my logo in PNG Format that have some complete transparent and some semi-transparent part and I'm unable to convert it in MBM without losing transparency and semi-transparency..!

So, Please help me on this, I'll be very thankful to you..!

Please mail me answer at: [email protected]

or post your answer over here

Thanks in advance...