Create a function in a separate script or module with SilkTest Workbench
From the properties pane of your VB.NET script you should go to select “Files” and right click to “Add File”.
Next you need to create a module or class which will contain the custom function. In the example below I have created a function which generates a random number based on a set of minimum and maximum parameters.
Finally you can then call the random function in the main module of your VB.NET script which executes your test case.