If text box exists in Expression builder?

[Fionn]

Hi, In a query I want to put into the criteria of a field

IIf(IsExists([Forms]![frmDailyClass]![txtTerm]),4,[Forms]![frmDailyClass]![txtTerm])"

But there is no IsExists only IsEmpty or IsNull and these both pop up a box asking for the value of txtTerm. Anyone know if there's a way of setting the value as 4 unless txtTerm exists and has a value in it? Thanks

[Dal Jeanis]

Are you attempting to test if the control exists? For instance, if your code is dynamically creating controls on a form at run time? Or are you just trying to determine if there is data in the underlying table?

If the control will always be there, and you only care whether there is data, then IsNull is a correct choice. That would look like this:

IIF(IsNull([Forms]![frmDailyClass]![txtTerm]),4,[Forms]![frmDailyClass]![txtTerm])

There's also a great function called NZ that was defined for exactly this situation, and allows you to efficiently override Nulls with your desired default value. That would look like this:

NZ([Forms]![frmDailyClass]![txtTerm],4)