excel formula help

[Fhyxx8]

I play dungeons and dragons, and we have a mostly blind DM.  i am seeking to write a formula in Excel to help track damage to monsters.  my thought is if he can enter the monster's hit points, and damage, his computer can automatically keep track for him, until the value reaches zero.  where i am falling short is getting the cell to continually hold the new number.  any help would be appreciated.   

Fhyxx8

[#2]

@Fhyxx8 

I'd enter each new value in a separate cell. Use a SUM formula in yet another cell to keep track of the total.

[#3]

@Hans Vogelaar 

thank you.

this will work, but it really isn't what I am trying to achieve.

what i am trying to do is make this simple for the user.

example:

I want to enter in the first figure (100)

then in another cell i want to enter another figure (10) 

i then want the first figure to reduce by the second figure, and hold that amount.  (first figure should now be 90)

i then want to be able to be able to replace the second figure, and have that reduce the new adjusted first figure, 

100-10=90, 90-10=80,etc...counting down to zero.

because he is sight impaired the easier for him to use this the better.  if he only has to enter in the first figure in the beginning, and maintain the second figure as needed, while the first figure automatically reduces to zero...then i believe it will help him stay organized.

does this make sense to you?

Fhyxx8

[#4]

@Fhyxx8 

In my humble opinion, that is not a good idea. Since it is not possible to see how the current value of the first cell came to be, it is very easy to make a mistake, and virtually impossible to correct mistakes.

If each contributing number is entered in its own cell, it's easy to check the end result and to correct mistakes.

[#5]

once the original number is entered in, it would become sacrificial...more or less. it would continue to count down until it reached the point of zero.

thank you for your help on this. I really do appreciate it.

Fhyxx8

[#6]

@Fhyxx8 

See the attached workbook. It contains VBA code (right-click the sheet tab and select 'View Code' to inspect it), so the user should allow macros when they open the workbook.