I have created .xls file from a database of another program.
But excel does not treat the data the way I want. Example:

in one cell there is a value 126:00

126 should stand for hours, 00 should stand for minutes

If I want to sum two cells I get #VALUE.

The format of the cells was "General", I changed it to format h:mm,
but nothing changed.

But when I double click the cell and then confirm with enter the cell
gets the right format and the sum of the two cells is correct.

How can I change the whole column this way?

stremetzky