Is it possible to generate an "end date" after entering start date and term length?

[Tim Mullin]

Hello all,

I'm hoping to find an answer to a question I have using forms in Access 2007.

I have a form (source: table) that has three fields:

Start Date
Term (number of months)
End Date

Currently the user has to enter a start date, select a term from a drop down combo box, and then enter an end date. Is it possible to have it set up where after the term is selected in the combo box the end date is automatically generated?

Any help would be greatly appreciated! thanks!

[NeoPa]

This is perfectly possible, but the idea of storing values that are calculable from existing data is not good (See Database Normalisation and Table structures for more).

The code to achieve this is :

DateAdd('m', [Term], [Start Date])

[Tim Mullin]

Is there a certain way I should format the input for the start date or for the term in the combo box? The current format is:

Start Date
Data Type: Date/Time
Input Mask: 00/00/"20"00;;_

Term
Data Type: Text
lookup box with the terms manually entered, not linked to another table (e.g. "1 month", "3 months", "12 months" and so on...)

when i pasted your code into the control source for the end date field it returned "#ERROR" in the field, but I'm assuming there is something wrong with the two fields mentioned above.

thanks again!

[NeoPa]

Tim, if you need a numeric value there - store a numeric value. You can probably extract a numeric value from the strings if you know exactly how they're formatted, but I can't as you haven't shared enough information with your three example values.

PS. The date as a date is fine and exactly as expected.

[Tim Mullin]

I got it to work! Obviously though there are issues with the data being stored, which you pointed out. I'm assuming there is no way to have it store that data?

[NeoPa]

There is nothing to stop you storing the data, except the understanding that it will not help you, and will likely involve you in extra complications. There will be no benefit from it for you.

I'm sorry. I guess that's not what you want to hear, but it's truth so I have to say it.

[Tim Mullin]

No worries, I came across this issue earlier in the database but figured I would ask again...

Thanks again for the help!

[TheSmileyCoder]

I would HIGHLY recommend changed your term text box to a combobox, in which the user can select a number of months. Having users manually typing things where precision is required is always a bad idea.
While it may be easy to write code to parse values such as "3 months" you will run into problems when you have users typing stuff such as "3", "3 mnths","3-6 months","3½ months","7mngts" and so on.

[NeoPa]

That's a good idea Smiley. I'd take it a step further though, and separate the value out from the units. It can be stored as a single text field if required, but the ComboBox would be better off simply allowing the selection of the units without any numerical values included.

Good thinking :-)

[colintis]

As from the example Tim provided earlier, there should be a fixed amount of choices for the term. If so, its better off to make selection with a combo box or option radio buttons.

[NeoPa]

You're right. Tim did start with a ComboBox rather than a TextBox control. Also, if there really is just a limited list of possible values, then a single ComboBox would be more appropriate. Separating them out would only be called for, for a large or unlimited number of possible values.

[Tim Mullin]

I do have the number of month choices set specifically in a combo box, however the resulting end date is too important with what we do to not have it stored, so I've gone ahead and removed the "auto-generate" function.

Numerous queries that use the end date as some sort of parameter that we need won't work (without more intense behind the scenes coding), so I think I'm going to leave it as a manual entry.

Thanks to everyone that replied, I really appreciate it!

[Tim Mullin]

Actually I take that back... I simply replaced the EndDate column headers in each of the queries with

EndDate: DateAdd('m',[Term],[StartDate])

and now they all work perfectly. Obviously as mentioned above having the data like this isn't the best way of doing it, however I feel that this is the best way to prevent the great deal of potential human error that could arise from manually computing the end date.

Thanks again guys!

[NeoPa]

Tim Mullin:
Obviously as mentioned above having the data like this isn't the best way of doing it,

obviously doesn't really work in this context. In fact the statement is wholly insupportable. Not only is that way the best way of doing it, it is also the only way that makes sense, unless all the brains that worked on the concepts of database normalisation are wrong and don't know what they're talking about. I won't be putting any money on that one ;-)