I am trying to add a CALCULATE FIELD condition.

I am trying to add a CALCULATE FIELD condition... i would like for the number of days between two dates to be calculated and then multiplied by a certain dollar amount (or number). And the total would then appear in an unchangeable field. Please let me know what to enter to have this done.

I start with

IF age group IS EQUAL TO 31-40

DO Calculate a Field's Value

DATE (End Date) - DATE (Start Date) * 1.08

SUMMARY Total Cost

We will be glad to assist you with this. You can create the condition as shown on this example: 

So, you will put the result in a Form Calculation widget. In regards to making the result read-only, please do the following:

Result: https://form.jotform.com/93008826547968 

Hope this helps.