SSRS check text to display value

I have two text values that I would like switch between if one has NA or N/A value or if nothing.So if Fields!text1.value is nothing or NA or N/A show Fields!text2.value else show Fields!text1.value

I tried using iif(Fields!text1.value = nothing, Fields!text2.value) but either I don’t have the syntax right or it’s just not working for me.

Does any have a way to handle this?