When to instantiate class object in do-loop

I use a class object named COMPANY.PART. This class has many properties and methods, among which is the ability to validate any given part number string for correct format, etc.

A typical use of this class would be;

dim oPart as new COMPANY.PART
oPart.Validate("some-part-number-string")

if oPart.IsValid then
do something nice
else
do something mean
end if

My question is when to instantiate the class when processing a large list of potential part numbers. Should it be outside of the loop logic or inside the loop logic? i.e;

(outside of loop logic example)
[i]dim oPart as new COMPANY.PART

while reader.read

oPart.Validate("some-part-number-string")
if opart.isvalid then
do something nice
else
do something mean
endif

end while[/i]

- or -

(inside loop logic example)

[i]while oreader.read

dim oPart as new COMPANY.PART
oPart.Validate("some-part-number-string")
if opart.isvalid then
do something nice
else
do something mean
endif

end while[/i]

Does it make a difference performance wise which way it is done?

Thanks.

Pat