The below are values in seconds and milliseconds.

28.921
36.432

If excel adds these values I get 65.353 If I change the format to
mm:ss.000 I get 28:19.200

I need to get 1:05.353. (ie 1 min and 5 secs etc) as these cells are
used in a formula. Does anyoe have any suggestions as I am stuck on my
sheet until I solve this.

Ps. I looked at len and tried some code that if the len < 6 then the
value was "00:" & cell.value but this didn't work - possibly due to my
code - but I was getting a decimal number in the cell.