I guess you want in C1: =A1*70% + B1*30%  Or something like that.

Tyro

I don't really follow what it is that you are askng.  If you want 30% taken
from B1, (ie 70% of the value of B1) then the formula in C1 would be:

=B1*0.7

or

=B1*70%

=============================================================
     About percentages in Excel

     Niek Otten, July 26 2006

     In Excel, percentages are stored as fractions; 15% is stored as 0.15, 100% as 1. That makes it easy to calculate with; just
multiply a number with a percentage and you get what you need. No need to divide/multiply by 100. In fact, if you see a
calculation with percentages which has the number 100 somewhere in the formula; be very careful, it might be wrong or at least use
percentages in a way they weren't meant to be used in Excel.
     The conversion to a fraction happens automatically if you enter the % sign: if you enter "15%" (without the quotes) the
value will be 0.15 and it will be displayed as 15%. If you then enter 12 in the same cell, two things can happen: It will be the
number 12 or 12%. What happens in your case depends on a setting:
     Tools>Options, Edit tab, "Enable automatic percent entry" (only Excel2000 and newer).
     All built-in functions of Excel and all the functions in Analysis Toolpak use this representation of percentages: be careful
when supplying parameters to these functions; never use whole numbers (like 8), always use fractions (like 0.08 or, even better,
8%).

     Frequently Asked Questions:

     Q:
     I have A1 and B1. How do I get C1 to show B1 as a percentage of A1?
     A:
     Formula in C1: =B1/A1, Format as %

     Q:
     I have A1 and B1. How do I show the difference as a percentage in C1?
     A:
     As a percentage of A1: =(B1-A1)/A1, Format as %
     As a percentage of B1: =(B1-A1)/B1, Format as %
     =============================================================

Percentages in arithmetic generally are fractions as well. "Percent" means
"per", Latin for "by" and "centum", Latin for 100. Therefore "by the
hundred" so, 15% is 15/100 = 0.15 and 234% = 234/100 = 2.34.  Let's not make
it seem like it's advanced Calculus. Duh!

Tyro