Polynomial Trendline Equation Trouble

This is the polynomial trendline equation I generated from a series of data
items. I've been trying for hours to write the equation properly in my
cells, but I do not seem to be doing it right. I'm a newbie at excel.

y = -3E-08x6 + 1E-06x5 - 4E-05x4 + 0.0005x3 + 3E-05x2 + 0.0101x - 0.0048
R2 = 1


Where x = percentage of job duration (B171/$D$165) (ex: .05)
and y = percentage of allotted hours used (ex: .006)


MY EQUATION:


=(-0.00000003*((B171/$D$165)^6))+(0.000001*((B171/$D$165)^5))-(0.00004*((B171/$D$165)^4))+(0.0005*((B171/$D$165)^3))+(0.00003*((B171/$D$165)^2))+(0.0101*(B171/$D$165))-0.0048

What am i doing wrong?... I'm getting negative numbers after plugging the
equation into my spreadsheet, so obviously I am re-writing the equation
wrong... Thoughts?

I may be getting too complicated here... and I think I am...

But I am looking to be able to make a spreadsheet that allows me to determine the amount of manpower needed in the construction business at any given time during the construction process. I have a set of values for every five percent of the job completion based upon industry averages.

For instance, at ten percent of the project completion, our company should have accumulated a set amount of hours (in this case, 1.85% of the total alotted hours)... At twenty percent of completion, we should have accumulated 6% of the total hours... I have "percentage of hours" values for every 5% of the projected timeframe. I want to be able to type in the length of the project (in weeks) and the total alloted hours for the project, and achieve a weekly hour value for each week of the project.

I've tried the IF command, but due to extreme variations in project lengths (6 weeks to 3 years) it's practically impossible to write a formula with a seven-condition limit using the IF command.

I figured that if I could graph my values, I could get an equation that would more accurately give me the results I am seeking. The graph that I get is not a straight line because, due to the industry averages our trade follows, the data shows that most of the hours used are in the middle of the project when things are going faster and more fluidly. The beginning and end of the project progress slower due to planning and completion tasks that occur. So I get somewhat of a nice fluid "S-curve".

If that is confusing, I apologize... I'm pretty new at excel functions... Thanks in advance for any input, advice, etc.

PERCENTAGE OF TIMEFRAME - ACUMULATIVE PERCENTAGE OF HOURS USED

05% - 0.60%
10% - 1.85%
15% - 3.65%
20% - 6.00%
25% - 9.00%
30% - 12.60%
35% - 16.90%
40% - 22.00%
45% - 27.80%
50% - 34.20%
55% - 41.15%
60% - 48.60%
65% - 56.35%
70% - 64.20%
75% - 72.20%
80% - 80.00%
85% - 87.20%
90% - 93.30%
95% - 97.50%
100% - 100%

Looks beautiful...!

However, when I try to change the weeks or hours, I get a #NAME error in the allocated hours column... I am supposed to be able to change these two values on your spreadsheet, right?...

Thanks again... The spreadsheet looks great!