Do you mean a static text element, or a command button? Actually, it doesn't matter because neither of these can be bound to a field.

Maybe you mean that you want to display the date from a (hidden) date field on a command button? That can be done. If that's what you want, you would use something like the following.

Label(MyCommandButton, @AsFormattedByLE(MyDateLE, 1, "")) 

The Label command is how you change the text on a command button (or a static text LE), and the @AsFormattedByLE command formats it the same as the date LE that we are getting the date from. Without the @AsFormattedByLE part, you would end up with a date that looks like "2012/10/30".

If that's not what you are looking for, please explain more about what you are trying to do.

A date field and a text box that is bound to a date field are not the same thing. I'm assuming it's the text box that you wanted to change into a command button.

Deleting an element and creating a new one of a different type that is bound to the same underlying field is the correct way to do that. For example, replacing a text box with a combo box.

Since a command button cannot display the dates in the date element, we're not sure what you are trying to accomplish by changing a text box that displays dates into a command button. Hence the confusion about answering your question.