Combining two values in two separate cells to make a cell reference or index ref.

I want to use a value in one cell as a row designation, and a value in another cell as a column designation. Ultimately, the values will be text which will refer to row and column headers. What formula would allow me to do this?

example:
A1 contains B
B1 contains 2
B2 contains "tribbles"

An imaginary function might go like this...

The formula in A3 is =SecondaryReference(A1:B1) [OR] =B2

A3 returns "tribbles"
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Ultimately, this would be done with text.

example:
"Multivitamin" is the header for column B.
"VitaminC" is the header for row 2.
B2 contains "500mg"

The imaginary formula in A3 is =SecondaryReference(Multivitamin:VitaminC)

A3 returns "500mg"
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I realize I'm probably leaving out some steps, particularly in the text idea. I'm just trying to communicate the idea of what I'm trying to accomplish. Is there a formula to accomplish this? Thank you to anyone who can point me toward a solution.

Welcome to the Board.

=INDIRECT(A1&B1)

Note: INDIRECT is Volatile (see link in Sig for more info.)

Thank you both. The first solution answered the first half of my question. The second solution answered the second half of my question. Both are awesome, and slightly embarrassingly obvious in retrospect. Even still, I worked on this for over an hour before giving up and going to the forum. Thanks for helping this exposed novice!