Replace null value

I have NULL value of data field, and I want to replace with '-' character in the crystal report. I try to write this formula "IIF(IsNull(table.field),"-",(table.field))", but the result still Null(blank). Can any body help me?
Thank'sOne option is to create a formula, and then place the formula in the report where the current field is located.

The formula would be:

if isnull(table.field) then "-"
else table.field|||Hi abstract, thanks for ur reply. Now i can fix the problem|||I don't think you understood what I was trying to explain. You need to create a Formula Field; NOT create a formula in the suppress box.

I have used this before, so I know it works.

abstract|||Never mind my last post, I misread something.

abstract|||I think this will work if it is in formula

IIF(IsNull(table.field),"-",(table.field))