Hello Pilo,
This VI ships with the PID Toolkit for labview and there should be examples with this toolkit. Here is useful link if you already didn't know about it that simply links to other documents explaining the use of this VI.
http://digital.ni.com/public.nsf/websearch/D820C25FA086026D86256D9E0078AF80?OpenDocument
simulating z transform within labview can also be done using the function wihtin the PID toolkit:
http://digital.ni.com/public.nsf/websearch/20946232F7FE728E86256DD8007814F8?OpenDocument
Hope this helps
Steven Bird