Subtract dates in same column

Hi,

I have 4 cols of data.

A = part number
B = Tester
C = Date
D = Weight

Parts are weighed and then weighed again after 2 weeks approx.

Can anyone suggest a formula that will subtract the weight on the second date by part number please?

jimde,

Welcome to the forum!
In your list, there are several part numbers that are weighed either only once, or more than twice (weighed up to 7 times in fact). What do you want in these cases? The difference between the two most recent weights? The difference between the original weight and the most recent weight? etc

welcome to the forum however....

Your post does not comply with Rule 1 of our Forum RULES. Your post title should accurately and concisely describe your problem, not your anticipated solution. Use terms appropriate to a Google search. Poor thread titles, like Please Help, Urgent, Need Help, Formula Problem, Code Problem, and Need Advice will be addressed according to the OP's experience in the forum: If you have less than 10 posts, expect (and respond to) a request to change your thread title. If you have 10 or more posts, expect your post to be locked, so you can start a new thread with an appropriate title.
To change a Title on your post, click EDIT then Go Advanced and change your title, if 2 days have passed ask a moderator to do it for you.

Your post does not comply with Rule 7 of our Forum RULES. Please do not ignore Moderators' or Administrators' requests - note that this includes requests by senior members as well, if you are unclear about their request or instruction then send a private message to them asking for help. Do not post a reply to a thread where a moderator has requested an action that has not been complied with e.g Title change or Code tags...etc

and "Problem with formula" is more descriptive of what you want than "Neat formula required"...how?

please rename your thread to something more meaningful, that actually describes your problem. lots of contributors will look at a thread title, and if it is of interest to them, or falls within their area of expertese, they might only open those threads. also, searching for "help" will not turn up too many results that will benifit you, sorry.
To change a Title on your post, click EDIT on you're 1st post, then Go Advanced and change your title"

jimde, you will not recieve any offers of help until you comply with the moderators request to change your thread title to something that actually describes what you want

yes, you have now, thanks

try this in E2, copied down...
=IFERROR(D2-VLOOKUP(A2,A3:$D$534,4,0),"")