spreadsheet: use equation to calculate value

Question

I have a simple table in Gnumeric (but I expect there should be a general solution for all spredsheets). Column B contains numbers (input), and column C should contain values calculated using my equation. For the first cell, the equation is =(B6-C5)*C4. Now I want to drag (expand) the equation down the column, so that all the cells are populated with the solutions. The problem is, the cells C5 and C4 should stay static, only the B cells should go from B6 to B_infinity.... But unfortunately, gnumeric increments all cells, ie

=(B6-C5)*C4
=(B7-C6)*C5
=(B8-C7)*C6
...

whereas, I need the equation to be:

=(B6-C5)*C4
=(B7-C5)*C4
=(B8-C5)*C4
...

How can I tell Gnumeric what I want ?

Answer 1

You can change the cell reference to be abosolute, with a $ symbol:

=(B6-C5)*$C$4

Answer 2

If excel is the same as gnumeric, you need to freeze your references. For the first formula, use:

=(B6-$C$5)*$C$4

After that, fill down this formula and it should be doing what you expected it to do.