in_array

Hello All,
Hope you are all experiencing some progress with yours.
Looking forward to some on mine. Have a quick question.

When traversing an multidimensional array what is the proper way to detect if a value is in one of the indexes of the array?

EG:

Array1 = array(
	0 => array("pUser" => "Customer", "pType" => "Offset", "pProduct" => "Business Cards"),
	1 => array("pUser" => "Retailer", "pType" => "Offset", "pProduct" => "Flyers"),
	2 => array("pUser" => "InHouse", "pType" => "Offset", "pProduct" => "Business Cards")
);

So I have this array and I want to add let's say a customer -> offset -> business cards, 
but let's also say that there is only 1 customer is allowed to offset print at a time.

How would I check for pUser, pType to see if one exists already?

I was looking at in_array(), but my brain twisted when the multidimensional came into play.
Not sure how to apply. Any help would be greatly appreciated. 

TIA.

Best,

Karl DeSaulniers
Design Drumm
http://designdrumm.com <http://designdrumm.com/>