Autofill 2nd date fieldon a form based on entry in 1st date field

I have two date fields on a form.  If the user enters, for example, 2/1/2015 in the first date field I want the 2nd date filed to auto fill with the last date of the month.  In other words this would be 2/28/2015 if it was this year.  Or if the user entered 4/1/2015 in the 1st field, have the 2nd date field auto fill with 4/30/2015.

What would the after update event be of the 1st field?
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Scott McDaniel (Microsoft Access MVP - EE MVE )Infotrakker SoftwareCommented:
You could do this in the AfterUpdate event of the First Date Field:

Me.SecondDateField = DateAdd("d", -1, DateAdd("m", 1, YourFirstDateField))

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Gustav BrockCIOCommented:
Or rather - if the day should differ from 1:

Me!SecondDateField.Value = DateSerial(Year(Me!YourFirstDateField.Value), Month(Me!YourFirstDateField.Value) + 1, 0)

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