Text field value - leading zeros dropped upon copy to another field

I have a text field that has numbers entered. There can be leading zeros (e.g. "010"). Fine so far. However, when the field loses focus (on blur), I run a JS to copy the value to a read only field elsewhere in the document. This script does NOT get any leading digits. I need the entire set of digits ("010" in my example) copied to the 2nd field (it's a phone # and unfortunately the document has the area code, exchange, and extension broken out into three fields, so I can't indicate it is a phone number).

I have tried custom keystroke script, custom validation script, custom calculation script, ... all to no avail. I can't believe no one has an issue with a set of digits dropping leading "0"s. My script that does the copying doesn't even see the entire string ("010"), but just the truncated one if leading zeros ("10").

Can anyone help??
Thanks, Mark