two Mishra's Factory and Blocking with one extra land

[Burr]

Situation: I have in play one island and two mishra's factory. My opponent attacks with two goblin lackeys. I tap my island to activate one mishra's factory and declare blocking on one goblin lackey. Can i then tap my blocking mishra's factory for one mana to activate my second mishra's factory and declare blocking on the second lackey with my second mishra's factory? If not, why not?

Thanks in advance

[Mark Sun]

Choosing which creatures will block happens in one step that doesn't use the stack.

Thus, during that time you can't activate the other Factory.

[hyc8028]

309.1. As the declare blockers step begins, the defending player declares blockers (this game action doesn’t use the stack). Then any abilities that triggered on blockers being declared go on the stack. (See rule 410, “Handling Triggered Abilities.”) Then the active player gets priority and players may play spells and abilities.

You have to declare legal blocker all at once. Your 2nd factory was not a creature at that time.

[Beatusnox]

Thanks guys, I was actually going to ask this question. Looks like I did get cheated out of first place at fnm then <_<

Attached to this though, on topic: If I block with a factory can I use another factory to +1/+1 after declaring it a blocker? Meaning, If I block with two factories, can I tap one of them to make the other bigger, so both of the opposing creatures are blocked, and one of mine gets the bonus?

[hyc8028]

Thanks guys, I was actually going to ask this question. Looks like I did get cheated out of first place at fnm then <_<

Attached to this though, on topic: If I block with a factory can I use another factory to +1/+1 after declaring it a blocker? Meaning, If I block with two factories, can I tap one of them to make the other bigger, so both of the opposing creatures are blocked, and one of mine gets the bonus?

Yes. Once blockers are declared, you are free to tap and use the factory's pumping abilities. You can use it pump itself, pump another factory. It is all legal.