please help me to put a formula in this cell?

the calculation in the cell E is based on the net change in F and G. For example "when i enter an amount in the cell F3, then it should add up with the amount entered in the cell D3. and likewise when i enter an amount in the cell G3, it should subtract from the amount entered in D3" ...... please help me with this as i dont know anything about macro vba ... :/enter image description here

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