Create a GP field in CRM (use a ‘money’ field)
Use the following code in the on-load or on-save event for the form:
crmForm.all.new_gp.DataValue = (crmForm.all.price.DataValue – crmForm.all.currentcost.DataValue);
The ‘new_gp’ field is the name given to the gp field you created.
This will then calculate the difference between the cost and price giving you the GP.