You will have to hard code the currency amount into the script.
In the first line, create 2 text fields, Text1 and Text2. Use this as the custom calculation script for Text2:
if(this.getField("Text1").value !==""){
event.value = this.getField("Text1").value * 100;
}
//Clears Text2 if nothing is in Text1
else event.value = ""
The second pair of text fields would have "50" instead of "100" in line 2, etc.