Hi @ysbaodnj. Here are a series of screen captured images and iLogic rule code examples to show a scenario like this working.
Here are the parameters in the parameters dialog:


Here are images of the global iLogic Form editor, showing the settings for both controls (parameters):


Here screen shots of the finished Form, with either value selected, and showing the resulting values for the other parameter.

Here is the internal iLogic rule within the document:

And here is the code within that rule:
'AB' is the blue, unquoted name of the one parameter, and due to the way we are using it here, any time its value changes, that will cause this rule to run. And when this rule runs, it will run the external iLogic rule named here.
oTrigger = AB
iLogicVb.Automation.RunExternalRule(ThisDoc.Document, "Toggle Multi-Values By Param Value Change")
And here is the code within that external iLogic rule named "Toggle Multi-Values By Param Value Change".
The first line is just getting the value of that triggering parameter from the 'ThisDoc.Document' document, that was specified by the other rule as the one this rule should be focused on. Then it sets a couple options / properties, then it checks the value of that initial parameter, and sets the available values of the other parameter accordingly.
Dim oAB As String = iLogicVb.Automation.ParamValue(ThisDoc.Document, "AB")
MultiValue.UpdateAfterChange = True
MultiValue.SetValueOptions(True)
Dim oValues() As String = {}
If oAB = "A" Then
oValues = {"1", "2", "3", "4" }
MultiValue.SetList("ValuesForList", oValues)
ElseIf oAB = "B" Then
oValues = {"5", "6", "7", "8" }
MultiValue.SetList("ValuesForList", oValues)
End If
Wesley Crihfield

(Not an Autodesk Employee)