Earlier (actually long back), posted a topic about placing Object prompt in the RS document/ RS Grouping;

Source: http://www.microstrategy101.com/?p=130

Here is the similar trick to use object prompt in the dataset created from Cube;

1. Create an object prompt with metrics (A, B, C, D)
2. Create a cube with attributes and with above A, B, C, D metrics and create a data set using this cube
3. Drag and drop object prompt from MicroStrategy Desktop window to the cube
4. And it works…..I tested this in 9.3 and 9.2.1 version.