C1 has a "Text" format and it contains: 123456

When I insert a new column (D), the format of its cells is (by default)
"Text".

In D1, I enter the formula: =VALUE(c1/100)

Because the format of D1 is "Text", D1 contains the literal
"=VALUE(c1/100)"

I then do FORMAT/CELLS, click GENERAL then click "OK".

When I press f2 and press "Enter", D1 now contains the value: 1234.56

However, if I later change the formula of D1, the "General" format
changes back to "Text" and it again contains the literal
"=VALUE(c1/100)"

How can I prevent the format from changing?