Loops, a basic question of performance

[Lunatic3]

Having this as refrence:

Dim i as integer
For i=0 to 1000
'Some code here
Next

Which one of the following will run faster? any as fast as the above?
1:

Dim i as Integer, J as Integer=1000
For i=0 to J
'Some code with no change in J value
Next

2:

Dim i as Integer, J as Integer=2000
For i=0 to J/2 ' Or any other operation on J
'Some code with no change in J value
Next

3:

Dim i as Integer
Const J as Integer=1000
For i=0 to J
'Some code with no change in J value
Next

4:

Dim i as Integer
Const J as Integer=2000
For i=0 to J/2 'or any other operation on J
'Some code with no change in J value
Next