How can you keep a reference to another cell from changing even if the other
cell's contents are moved?

The objective is to maintain a column of running summations, such as a
projected bank balance, that refer to anticipated credits or debits in
another column, even as those entries are moved about.

For example, cell G100 has the formula =SUM(D$4:D100), which works only
until the value in D100 is moved, say to D150, whereupon the formula in G100
is automatically changed to =SUM(D$4:D150). I can copy and paste the value to
D150 and then just delete the old value in D100, but this is cumbersome when
lots of figures are being moved around to effect an optimal result in column
G. I would rather move the values.

Can this be done in Excel?

Thanks,
Tim