I wont give you the code, but Ill tell you what you've got to do;
- Get the mouse's x and z screen vector using Pick Screen
- Generate the mouse's x and z positions in 3D Space whith the value you just got
- Use the Get Ground Height() command, giving it the x and z coordinates you just obtained and the matrix number of the matrix you're working with, this will generate the y position of the object you're placing.
- Position the required object at the x,y,z coordinates obtained from the above.
Look up those commands in the help file, to convert the vectors to positions you're going to have to look at the GET PICK VECTOR() commands, the help file goes into some detail explaining the use of the Pick commands and how to obtain 3D world coordinates from them.
Goodluck,
- RUC'