S7 Standard PID FB, FB41

I am familiar with Step 7 and troubleshooting of PLC logic, but I have never designed a PID Loop. I am wanting to use Siemens Standard Function Block FB41 (Cont_C) and I have no idea how to do so.
Specific: I want to control an output to a fisher control valve (4-20mA) for temperature regulation. The twist is I need to control the process to 100 degrees F until I see another digital input (flow) and then ramp up to 140 degrees F. Feedback by thermocouple (4-20mA). No valve position feedback.
My question is, does any one have a good explanation of FB41 terms and inputs… notice I said good, as in a newbie to PIDs could understand? Or does anyone have any suggestions of the best way to go about tackling this logic.
If more info is needed I will be glad to post.
Thanks in advance

I just finished programming a few FB41s. To get good help, do the following:
Open up an S7 program. Open up OB35. Insert a FB41 in a new rung. Place your cursor over the block and press F1. A help page for FB 41 will open up. It is very good. It has all the help you will need.
In regards to your specific need to ramp up the temperature, you need to write a line of code which conditionally moves a setpoint of 100 or 140 degrees to the setpoint input of the block. The setpoint needs to be a Real number scaled 0-100. The process variable can be an analog input. This would be something like PIWxxx. You need an enable bit to turn the block on. You need a Gain input. This would be a Real number. You need a reset input. This would be formated as a TIME input. You may or may not need derivitive action. The output gets moved to an analog output. Something like PQWxxx. Try that for starters.