Some very simple excel questions from a beginner, please help me out.

Hi, we need a spreadsheet for our home budget and businesses. Im using excel 97 and have made a rough sheet up but have some problems.
1- How do I make a formula "wait" until all the cells its formula depend on are updated by my weekly input ie- c3 is =b1-b2-1000 as soon as I input into 1 of these cells c3 will update which gives me incorrect info.
2 How do I "reset" a whole work sheet? ie: set all values in all cells to zero or at least on a cell by cell level, and keep the formulas intact?
3 how do I enter a value and have it subtracted from another cell which already has a formula in it. ie a1 =b1+b2 how do I input a value into say d2 and have that value subtracted from a1 without upsetting the formula in a1
4 when I cut and paste any cell in my spreadsheet all the formulas update themselves and add and subtract their totals according to their purpose and all I was doing was moving cells around. How do I stop this.
thanks for the help