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Convert the string to a date and use the weekday function?<br />
<a href="https://support.microsoft.com/en-us/office/weekday-function-05d360d7-2c3f-4691-9448-c96ea0351940" rel="ugc">https://support.microsoft.com/en-us/office/weekday-function-05d360d7-2c3f-4691-9448-c96ea0351940</a>
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So, this is more of a complete Access coding question?<br />
<br />
When do you want this alert to fire?<br />
When leaving the field, when submitting the form, when?<br />
<br />
How do you want to alert the user? &nbsp;popup, general message, format their hard drive?<br />
<br />
Possibly a quick validation rule?<br />
<a href="https://support.microsoft.com/en-us/office/restrict-data-input-by-using-validation-rules-b91c6b15-bcd3-42c1-90bf-e3a0272e988d" rel="ugc">https://support.microsoft.com/en-us/office/restrict-data-input-by-using-validation-rules-b91c6b15-bcd3-42c1-90bf-e3a0272e988d</a><br />
<br />
Pay attention to this piece of the doc:<br />

<blockquote>
What you can put in a validation rule<br />
<br />
Your validation rules can contain expressions — functions that return a single value
</blockquote>
<br />
Specifically <b>functions that return a single value</b><br />
<br />
If you look at the weekday function, it returns a single value...
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SteveL13

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One minor change...<br><br>Cancel = (Weekday(Me!WeekStartDate.Value) &lt;&gt; vbSunday)
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<div class="content wysiwyg-content fr-view">
On a form I have a field named WeekStartDate. &nbsp;How do I warn a user if the date they entered is not a Sunday?
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On a form I have a field named WeekStartDate.  How do I warn a user if the date they entered is not a Sunday?

How do I warn a user if the date they entered is not a Sunday?

Microsoft Access is a rapid application development (RAD) relational database tool. Access can be used for both desktop and web-based applications, and uses VBA (Visual Basic for Applications) as its coding language.