How to remove certain number of characters from either right or left for a string?

Hi there,

I need to remove a certain number of characters (such as 3) from a string from either ends.  I have tried TRIM, SUBSTR and nothing works.  There must be a way to do it.  Please help.

Here is an example:

Two values:  123456700000 and 123456000 and I want to remove only 3 zeros from right, not all zeros, so that I get: 123456700 and 123456.

Thanks,

Ning