You have only ask for a block with retentivity. I wrote to you which block.

But I don't know what exactly you want to do.

You have to select Mode 3 by this block.

So is my question now: What exactly want you to do?

Have you read the online help for the "Max/Min" block?
It explains exactly how the block works.

But I don't understand the point.
Why do you want to store the value right after the analog amplifier? Is that supposed to be some kind of set point? If yes, what is the condition to save?
If the value is to be saved once, e.g. by pressing a button.

That's what I meant by: Explain exactly what you want to do...