I am creating a Userform to input information into a sheet. The hardest thing I need it to do right now is calculate an assay and auto update a text box inside the Userform. In further detail, say I have three boxes (A, B, and C), these boxes should add to 100. I want to be able to input values into A and B, while C updates everytime these two change to show the remaining value out of 100. So initially it would display 100. Then if I enter 20 into A, as soon as I press enter or click B, it updates to 80. How would I go about doing this?