Creating a search text box in an Access 2013 Navigation Subform

I created a search text box in Access 2013 that works as in should in the form. When I moved the form to the Navigation form it stopped working. I receive the following error: "The action or method is invalid because the form or report isn't bound to a table or query." I have changed the condition in the Embedded Macro to read as follows:

[conLastName] Like "*" & [Forms]![frmNavigation]![NavigationSubform].[Form]![TxtSearchContacts] & "*"

I have also tried:

[conLastName] Like "*" & [Forms]![frmNavigation].[NavigationSubform].[Form]![TxtSearchContacts] & "*"

And:

[conLastName] Like "*" & [Forms]![frmNavigation]![NavigationSubform]![Form]![TxtSearchContacts] & "*"

Any and all insight would be greatly appreciated. I have spent well over two hours beating my head against the wall on this one. Thank you. ~Christa