Is there any way to differentiate Null (Which represents absence of value) &

Is there any way to differentiate Null (Which represents absence of value) & Space ( Which is actual a value instead).

I have a requirement where in SAIL FORM's Textfield is Null First time but after putting value into it and then with Previous button concept in further Forms, update it with Space in First Form.

In an expression it is treating Null & Space as a same value....

OriginalPostID-133273

OriginalPostID-133273