Does anyone know how to break links to an external file but still keep
the formula?

For example

if I had a formula as follows: ='[some external file]sheet1'!A1 *
5000. Assume '[some external file]sheet1'!A1 = 100.

I would like the value of 100 * 5000 in the cell

If you use Edit- Break Links, then it just puts the value in the cell
(500000 in the case above).