To add parametric variable,use PARAM part from special.olb library.
Place PARAM part. Double click it.
Below first tab is command button "New Property...". Click it.
Add parametric variable name and default value, click ok.
Close "Add New Property" window. Click "Apply", which is
next to "New Property...".
Next, in schematic, double click part value you want to make parametric.
I.E. for caps you can double click cap value, and type property name
inside curly brackets, like {CapVal}.
Now, cap(s) with value {CapVal} will have capacitance you
put under (default) value in "Add New Property" window.
Sweeping is done under menu "Pspice"->New/Edit Simulation profile"->"Analysis",
under options check "Parametric Sweep". Select "Global Parameter". Under "Parameter name:" type variable name without brackets. Under "Sweep type" select type:linear,logarithmic or value list.
