You should use and ArrayList control.
With ArraList1.Sort(cNumber) you sort numbers.
ArrayList1.Item(0) contains the min value
ArrayList1.Item(ArrayList1.Count-1) contains the max value.
You must be careful with the variable declaration:
Dim Arr (100) As Byte
Byte is an unsigned integer !
But tinmanjo has also negative numbers.
The most suitable variable type with B4PPC 6.90 is Number, you could also use Integer, but B4PPC will convert the Integer variables to Number variables for the calculations.