Fill in form to type Item descrictions and costs and fill in funct
 

Supposing that I have this picture of entrance of costs
A B C
1 Item Cost Input Cost accumulated
2 Item 1 100 100
3 Item 2 200 300
4 Item 3 300 600
6 €¦€¦. 600 1200
7 Item 1000 1000 2200
2200
And that intend to insert a new item with the command to insert line to fill
out the cells A and B


A B C
1 Item Cost Input Cost accumulated
2 Item 1 100 100
3 Item 2 200 300
4 Item 3 300 600
5 Item insert545
6 €¦€¦. 600 600
7 Item 1000 1000 1600
2745

Note that a accumulated value is not correct

It is necessary to enter automaticaly C line value with accumulation
function filled downing. But we need it doing with formulas protected.
A B C
1 Item Cost Input Cost accumulated
2 Item 1 100 100
3 Item 2 200 300
4 Item 3 300 600
5 Item inserted 545 1145
6 €¦€¦. 600 1745
7 Item 1000 1000 2745
2745
How can we that for people to type in the values have not to change formulas?