Is There A Function To Change Product Price Before Add To Cart?

Multi-Vendor Questions
1

my client want to change price before add to cart...

based on product size select... but size is not predefined is increase 1 to 1000s

i have tried what i see on internet but nothing is working till..

2

Your request is not quite clear to us. Could you give an example?

3

my client want to change price before add to cart...

based on product size select... but size is not predefined is increase 1 to 1000s

i have tried what i see on internet but nothing is working till..

Do you want to show new price before the Add to cart button is clicked?