Uhh... use the help file?
Then again, you could be using a trial version, or a cracked trial version (shame on you!!), so I'll copy it out of my DBC v1.13 help files.
Quote: "
SET MATRIX HEIGHT
This command will set the individual height of a point within the matrix. To raise a whole grid square you would need to raise four points, one from each corner of the square. If you set points x=0 z=0, x=0 z=1, x=1 z=0 and x=1 z=1 to a value of 10, you would raise the near left square upwards by ten units. The matrix number and tile reference values should be integer values. The height value should be a real number.
SYNTAX
SET MATRIX HEIGHT Matrix Number, X, Z, Height
"
Enjoy.
How's my typing? Phone 0800-GO-TO-HELL