I'm not sure about the concept of removing spaces before an amount since the size of numeric fields (if you are using numeric fields) is normally self regulating and right justified, but other than that have a look at the TRIM related functions - TRIM, LTRIM, RTRIM. In V9 perhaps INTRIM although your immediate needs seem more specific than that.
Edit: Should have added that you need to create a calculated field to do this.
If your desired end result is a numeric field and you're starting with a character field, you will need to use the Val function. The Val function handles the removal of any leading or trailing spaces by itself; you won't need to use a Trim function.
But as Grant mentioned, you will need one of the Trim functions for character fields.