Unable to edit the dimension of virtual part after deleting external equations.

Hi, I am facing a problem in soild works top down design.

I am unable to edit the dimension once external equation for that dimensions is deleted.

Hear the detailed explanation...

1. I created a assembly which contains virtual parts.

2. I defined some equation in the assembly file(GLOBAL) and linked this equtions to the part file dimensions via parametric modeling.

3. Now i want to repace these dimensions with design tables.

4. To do so I deleted all the equations.

5. While remaning the part dimensions(extrude height) I am unable to edit it and it gives a message saying "dimension is read only".

Please suggest me how can i modifiy or edit my dimension with out read only error.

Even I can not modifiy the value too.

Thanks and Regards,

Babu Rao K