>When I want to check the this.text in combobox it shows the data with dashes.
>How should i get this.text without dashes.

Get chrtran(this.text, "-", "") instead.

>I also want that the data i enter in combo should be valid, which is already in combobox. I think you understand what i mean.

The values in the dropdown? They will come from any source you give it - an array, field in a table etc. So you make sure they are valid before feeding them into the combo.