Windows 7: Excel: How do I make some cells remain the same when pulling it down?

Been having some problems with excel getting it to behave like Iwanted, tried google around but so clueless as to what to call things that it makes it hard. What I want is for a cell formula to do as I want when I pull on the lower-right corner down. Normally it the adds 1 to every cell address, but I need some of them to remain the same while others change. More exact:

I'm trying to make excelsheet where one collum is supposed to have the formula:

=F3*Dx/D3

x goes from 3 to eternity, while F3 and D3 should remain static while doing that drag thing. I remember there was a way to mark F3 and D3 so they don't change, but can't remember how.

So F4 has F3*D4/D3, F5 has F3*D5/D3 and so fourth.

You want to change your formula so it looks like this: =$F$3*Dx/$D$3
This will cause the Dx reference to update as you copy the formula from cell to cell but the formula will always use the cells F3 and D3. Putting the $ in front of the cell value tells Excel not to change that, it's called an absolute reference. You can use $F$3 which locks the column and row, or $F3 which locks the column only while F$3 would lock the row only.

Strollin is 'absolutely' correct.
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Switch between relative, absolute, and mixed references - Excel - Office.com