How to allow input of any decimal places in number format field on a form

[Ann_Elain...@adobeforums.com]

Using Adobe Acrobat Pro 7.0, I am creating a simple Purchase Requisition form. "Cost" field can be 2, 3 or 4 decimal places. Cost will be used in a calc, e.g. ("Qty" * "Cost") = "Amount". I will put the calc for Amount in custom calc with JavaScript so if result is zero I will show "". (Found code in another forum--very helpful.) Qty and Cost must both be numbers but it seems I'm forced to pick one choice for decimal places. Is there Javascript code I could use in custom format to allow/display from 2 to 4 decimals, not show 4 all the time? I am a complete novice in Java. thanks.