I currently have the following for some mandatory fields:

$Mandatory_Fields="*Customer Name*Customer Email*Phone Number*Payment 
+Method*BillingAddressLine1*BillingCity*BillingPostCode*CardStartDate*
+CardIssueNo*CardSecurityCode";
[download]

Idealy I would like to make the CardStartDate, CardIssueNo and CardSecurityCode only mandatory if credit card as a payment method is selected. Is there anything like an immediate if I could place in there to only make these mandatory if a radio button is true? I hope I have explained this clearly. Thanks as always. Simon