Advice needed to speed this code.

[p45cal]

concerning the dependency of the calculation within the grid, its difficult to remove as it shall take into consideration what qty has been planned previously and calculating the remaining qty to planned. That is why it will depend on the previous value calculated on the grid. I have try to figure out it this can be done in another method but still has not been able to.

example if we have 2,500 mins in total to plan with a min minutes per day of 450 it will be calculated as follow :

day1 day2 day3 day4 day5 day6
450 450 450 450 450 250.

Thus it will always check the cumulative planned previously to plan the qty remaining.

It is all right for the formula to check on other cells within the grid (it does this for previously calculated cells to the left and above a given cell in the grid).
It is not OK for the cells in the main grid to use cells outside the grid, which in turn refer to cells within the grid in their formulae.

You need to check the formulae in the cells outside the grid which your original formula referred to and:
1) See if they can get their data from outside the grid
2) Or see if they're needed at all in the original formula, or whether the equivalent info can be gained from elsewhere (outside the grid).