Excel Formula help

Hi

Please would you be able to help, I am very new to excel having only used it for basic functions, I am now expanding my knowledge and designing a spreadsheet to help with delivery schedules etc. I would like to add some more automated functions. In column J, I would like to know if I could program excel to test for any value in the cells in this column (text or number) and change the values in C,D,E,F,G and I columns to blank, put the day the task was complete into column M, and the data in column D into column N.

I also have an issue with column F because of the date formula used. When column C does not contain a date value, it reads the cell as a zero, the formula takes this value and compares it to B2 which leaves column F with a negative value and looks messy, is there anyway to clean this up? (I have used a temporary fix by formatting the Cells in that column (0; this again stops me from looking how overdue a delivery is.

Last but not least, I wish to add a third statement to column G, (Due Today)

Thanks for any help, its greatly appreciated.

Regards