Trying to figure out an expression to convert numbers that are 4 digits to 5 digits beginning with 0.

Such as 1605 to 01605

While at the same time leaving 5 digit numbers alone such as 16058 as 16058

Not certain how to go about using the len or if I even need to gather the length of the number.

for i in 0{1000…9999} {10000…99999}

???

Just wanting to:

take the value from a numeric text field box

add a 0 to the beginning of the number if 4 digits in length to make it 5

then have it available to be bound to another numeric text field box

Any thoughts of how this could be accomplished?