Sets/changes a distribution you have defined.
The sequence of the parameters for each distribution type in this command is always the same as the sequence in the interactive dialogs that set parameters of distributions. e.g. for a "Normal" distribution, Parameter 1 is the "Average" and Parameter 2 is the "Std Dev".
In the below example, a Named Distribution has been created and called "dummy". It has been set to Normal Distribution with an Average of 30 and Standard Deviation of 4. As there is not a 3rd or 4th Parameter, they can both be set to 0.