[fpc-pascal] SetLength procedure

[Steve Gatenby]

Could anybody enlighten me on how to make the 'SetLength' procedure into 
an equivalent function

I have many instances of
   SetLength(xxx, Length(xxx)+1);
   Num := High(xxx);

I would like to have Num :=  SetLength(xxx, Length(xxx)+1);
  or even something like Num := IncLength(xxx, 1);

These are on varying types of array, so not really feasible to create a 
function for each one.
Hoping it is possible within pascal itself :)

Thanks - SteveG