trying to find a calculator with a scroll key function.  I have a
Texas instrutment one but it is broke and I cannot repair it

Hello janice3536-ga

I tried to locate another Texas Instruments calculator for you, as
some folks get accustomed to certain brands (other manufacturer's
scroll keys may not work *exactly* in the same manner). I sourced a
Texas Instruments TX 30X IIS

It is reviewed at epinions.com
http://www.epinions.com/offc-review-1313-B613900-39C2D22C-prod1
'dzachsie' on the Sep 15 '00, writes:
"It has a scroll button, and built in memory. This enables you to
scroll up to problems you have been working on in the last few weeks."

The TX 30X IIS  is available from Amazon priced at a very reasonable
$14.28
http://www.amazon.com/exec/obidos/ASIN/B00000JBNX/epinions/002-4238902-3964033

Or a more powerful Texas Instruments calculator the TI-83 priced at
$98.64 (note the scroll keys in the picture)
http://www.amazon.com/exec/obidos/tg/detail/-/B00001N2QU//002-4238902-3964033?v=glance&s=electronics&me=ATVPDKIKX0DER&vi=pictures&img=14#more-pictures
Described here on Amazon in the Editorial Review
http://www.amazon.com/exec/obidos/tg/detail/-/B00001N2QU/002-4238902-3964033?vi=glance
"displays graphs and evaluates tables on a split screen, allowing you
to trace the graph and scroll through table values simultaneously"

A different brand, Casio CFX-9850GB with additional graphing
functions, has scroll keys too priced at $84.99
http://www.amazon.com/exec/obidos/tg/detail/-/B00004TVDN//002-4238902-3964033?v=glance&s=electronics&me=ATVPDKIKX0DER&vi=pictures&img=14#more-pictures

I hope that helps, if you need any clarification of this answer, just
ask.
Kind regards
lot-ga