Try this:
Left([dimension]; 2) + ":" + Substr([dimension]; 3;2) + ":" + right([dimension]; 2)
This assumes that the string will always be 6 characters long - two for hour, two for minutes, two for seconds with a leading zero for each if it is less than 10 (like 010101 for 01:01:01)
-Dell
A computer only does what you actually told it to do - not what you thought you told it to do.