How to create metadata dynamically at runtime ... in odata service

Hi experts

In one of my requirement my entity type has 10 fields, so in $metadata i will  get 10 fields in the properties.

But from UI side they want only 5 to 6 fields, selecting fields is done at the runtime,

So is there any way to change the $metadata properties at runtime, so that we can send only selected fields from backend in $metadata properties

Any chages is need to made in MPC_EXT class define() method .

Ex:-

Consider Employee  entity type having 10 fields, if user selects one option, i have to send only 4 fields in the properties of $metadata

.

If user selects another option, we need to send 8 fields in the properties of $metadata .

Any way to do it ... ??

Thanks .....