Automatic percentage calculation of value but in the same cell value being entered

Hi,
I want the cell (in which I type some numerical value) to show a certain percentage of the entered value (say 40 %) but in the same cell instead of actual value entered. For example if I type let say 100 in the cell A1, the same cell should now show a certain percentage of the entered value (say 30 or 40 % whatever required) instead of showing the entered value. Like in cell formatting, we can program the cells to show the entered values in different styles/ways but underlying actual value remains same.

Not without vba (a macro).
Cells A1:A10 will behave as you might want (the underlying value changes). Few checks and balances, no bells and whistles.

You can do it with the camera tool.

Say your input is in A1 on Sheet1. In some other cell, say A1 on Sheet2, put the formula =Sheet1!A1*40%.

Then you the camera tool to image that cell, and move the image over Sheet1 cell A1.