Besides Harry's suggestion (and his apparently less serious or even sarcastic further suggestions), 'look-in function' or perhaps even 'reference function' might work here -- the former particularly in a spreadsheet context. Try googling it, with or without the hyphen...

If your audience is real software nerds (ahem, programmmers). AFAIK the term originates from the original Basic programming language, which had (and still has) the 'peek' and 'poke' functions for reading or writing from or to a particular location, and it has been generalised (e.g in C and C**).

sample refs:

infile.peek function - C++
infile.peek function C++. ... You're currently browsing the C++ section within the Software Development category of DaniWeb, a massive community of 288820 ...
www.daniweb.com/forums/thread97597.html - 44k - Cached - Similar pages
PEEK and POKE - Wikipedia, the free encyclopedia
The PEEK function and POKE command are usually invoked as follows, ... itself (making possible the software implementation of powerful machine code monitors ...
en.wikipedia.org/wiki/PEEK_and_POKE - 28k - Cached - Similar pages
I am getting errors using the Peek() function in C# for a file ...
I wanted to test out the Peek() function so I first read in the int value and then called ... Programming & Design · Security · Software · Other - Computers ...
answers.yahoo.com/question/index?qid=20070305154247AAjyiw9

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Note added at 11 hrs (2008-03-08 21:17:00 GMT)
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oops: C++