So i want to make a formula that stays at its cell. I want to make the electrical U=R*I, R=U/I and I=U/R.

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When i input something at U and R i want I out. If i change the value at I and U, it shall give me the right R value. So i want back and forth formula. Like those
arrows that come up when you do for example:
G11=G12*G13
G12=G11/G13
G13=G11/G12

Then some blue arrows come up to tell us that one Cell is dependent on another. How do i make it permanent, so the formulas stay in the cells, even if i replace them. I just want the it easy: I know 2 things, and i want the third. I put in U and I, to get R. I know R and U, to get I.