yes, you can ad multiple functin calls to an onclick evenet. But, it may not be the most efficient. For example, if validation fails you don't want to continue. So, it wouold make more sense to have one function, if it passes, to call the next function.
I still don't understand why you are copying this to the clipboard. I thought you were using the form to post the data. Also, you could set up a global variable to set the fields and preferences for validation instead of passing all that data in the MM_ValidateForm function.