Storage Counter Lands

[No_Life_No_Future]

There is one for each color but i just used this as an example:

Hollow Trees
Land
Hollow Trees comes into play tapped.
You may choose not to untap Hollow Trees during your untap step.
At the beginning of your upkeep, if Hollow Trees is tapped, put a storage counter on it.
T, Remove any number of storage counters from Hollow Trees: Add G to your mana pool for each storage counter removed this way.

If another sorce gave it a mana ability (for example Tomb of Yawgmoth/Riftstone Portal) could I tap this land before it checks to see if its tapped at the begining of my upkeep to add mana and still get a storage counter?

I think its a triggered ability, so I could respond it by tapping the land to use it to add to play instants during my upkeep while still ramping up mana like a pro :)

[parallax]

No. This is an example of an "intervening if clause". It will not go on the stack in the first place if the condition is not met. It will also check upon resolution to make sure the condition is still met. The land must be tapped at the beginning of your upkeep and when the ability resolves.