Hi Ladybug726,

Not sure I understand everything you are trying to do, but here are some
comments.

Col A - Parts, Col B - Qty, Col C - Cost-1, Col D - Tax, Col E -
Multiplier,
Col F - Subtotal, and Col G - Cost-2 (or Total). I have formulas in Cols
C-D-F-G to calculate. Column E - Multiplier, is where I need a list box
to
appear so the user can tab to that cell and select the percentage from the
list box and have that number inserted automatically into that cell, then
the
next cell calculations will be done automatically, as well. (If, of
course,
I have done the formulas correctly.)

There are actually three types of list boxes that you can embed in a
worksheet. I will take a guess and describe wht=at I think you need.

Lets' say your list is in Sheet2 range A1:A4, and the data you describe
above is in Sheet1.
Enter the following values in Sheet2 range A1:A4
0.1,0.2,0.3,0.4 Format the range as Percentage.

The easiest listbox for your purposes is the cell validation list. To use
this, select some cells in Column E - Multiplier in Sheet1, then use the
menu command Data - Validation...
Change the validation criteria to List. Then click on the source box and
select the list range from your worksheet (or just type =Sheet2!$A$1:$A$4).
Click OK.
Now, if you select one of the cells that you have applied Validation to, you
will see an arrow - click on this to see the list box. You will need to
format the cell as Percentage to see the correct rresult.
Copy the cell down as far as you need.

Ed Ferrero
http://edferrero.m6.net/