Well, there are a number of things here. First of all, you can always control which buttons are shown and you also have control over their enabled states. You can also determine if a page is a Finish page (forced) by setting the NavigationType of a page to FinishPage.On the wizard control itself, you can control each of the buttons through the ButtonSettings (i.e. BackButtinSettings, CancelButtonSettings, etc.). You can then use the Show properties to determine if they will be shown (i.e. ShowBackButton, etc.).
Finally, the wizard control has a method to control the enabled states of the buttons:
this.wizardControl1.SetNavigationButtonStatus(MicroFour.StrataFrame.UI.WizardNavigationButtons.Back, MicroFour.StrataFrame.UI.WizardNavigationButtonStatus.Enabled)