Formular to subtract a number per day

You will need to provide more info... if for ex. you mean you want to do something along the lines of say:

subtract say 2 from the value specified in A1 for each day passed since the date specified in B1 up to today then

C1: =A1-2*(TODAY()-B1)

Have you stored the warranty dates themselves ? You could then use a Formula to calculate days remaining based on current date. A sample file would help.

If there is no date to compare to the computer won't know as to when a further 1 was to be subtracted from the existing values unless the file runs 24x7.

Again, guessing having no file to work with, I would suggest you use a Workbook_Open event to compare the current date to a cell containing the last date the values were updated and if the difference > 1 day then reduce all values by the number of days having passed since last update, the date cell itself is then updated to reflect the fact that the current day calculation has been performed.

for sake of demo. let's assume you have numerical values in B1:B100 which are to be reduced by 1 each day, in C1 we have a static date stamp to indicate when the values were last adjusted, let's initially set to say 04-Aug-2009 (yesterday).

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The above would reside in ThisWorkbook Object in VBE.

Yes as expected, you need to store the last date the values were updated (say F1), then run some VBA when the file opens as suggested, however, you have a bigger problem in so far as you have multiple day values within one cell (eg 113 & 843) if this can't be avoided the approach would need to be adapted from that advised previously to something along the lines of:

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Again the above would reside in ThisWorkbook object model and would be invoked when the file was opened (Macros must be enabled obviously).

Using your sample file as you uploaded (do this on a copy rather than the real thing until you're comfortable with what happens):

Into Cell F1 on Sheet1 enter the value: 04/08/2009

Right Click on the XL icon next to the File Menu and select View Code and into the resulting window paste the code given in my penultimate post. Save your file.

If you now close & re-open your file (enabling Macros) you should find all the values in column D reduce by 1 and the value in F1 updates to today's date (05/08/2009) .. the values in D will only adjust on open where the date in F1 is less than today's date (ie when a catch up the reductions is required).

see attached - note I left F1 as today's date initially such that when you open the file the values do not alter initially... to re-test you would alter the value in F1 to say yesterday's date, save the file and re-open and the values should adjust accordingly.

To reiterate it is essential that Macros are enabled in order for you to use this approach.

EDIT: file reloaded at 13:07 UK time

Originally Posted by aliii

what is the formula, that subtract number daily or each 27 monthly e.g

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