Modules & VBA :: Pull One Max Date From Value In Four Different Text Boxes On Continuous Subform

We're looking at a way that we can easily display what stage our clients' email marketing campaigns are at - in one section of our CRM our Campaign Manager will enter information on whether the campaign has broadcast (ie: emailed out to the required circulation list(s)), if we're waiting for artwork from the client or if we're chasing for that information.

I have four text boxes (date format) hidden on a subform that I need to pull ONE max date from.

So, as an example:

Email1 (our first email to the client chasing for artwork) = 01/01/2015
Email2 (our second email to the client chasing artwork) = 08/01/2015
Email3 (our third chase email) = 15/01/2015
Broadcast (the date the email campaign was finally sent) = 29/01/2015

I would need some code to show in an unbound textbox "Broadcast: 29/01/2015"

But, on the other hand, if the dates looked like this:

Email1 = 01/01/2015
Email2 = 08/01/2015
Email3 = Null
Broadcast = Null

I would need some code to show the following in an unbound textbox "Last Chased: 08/01/2015"

So we can easily see the status of our marketing campaigns at any stage in the process.

I've tried using IF THEN ELSE statements in the subform's On Current event, but that populates the information from the record you've selected across all the other records on the sub as well.

So I'm wondering if it's worth setting the Control Source of the unbound textbox I want to display the campaign status in as a bunch of nested IIF statements instead?