[Run]
Filename: {tmp}Setup.exe; Parameters: /ProductNames=product1,product2,etc...; Flags: shellexec WaitUntilTerminated; StatusMsg: Installing products...; Tasks: product1 and product2 and not product3 etc...

[Run]
Filename: {tmp}Setup.exe; Parameters: /ProductNames={%var1}{%var2}; Flags: shellexec WaitUntilTerminated; StatusMsg: Installing products...;

[Code]

var
product1: string;
product2: string;

procedure TaskOnClickCheck(Sender: TObject);
begin
  product1 := ''
  product2 := ''

  if IsTaskSelected('product1') then
  begin
    product1 := ',product1 Name'
  end;

  if IsTaskSelected('product2') then
  begin
    product2 := ',product2 Name'
  end;

end;

procedure InitializeWizard();
begin
  WizardForm.TasksList.OnClickCheck := @TaskOnClickCheck;
end;