%MSECONDS(number)
%MSECONDS converts a number into a duration that can be added to a time or timestamp value.
%MSECONDS can only be the right-hand value in an addition or subtraction operation. The left-hand value must be a time or timestamp. The result is a time or timestamp value with the appropriate number of microseconds added or subtracted. For a time, the resulting value is in *ISO format.
You can also use %SECONDS to add or
subtract microseconds or any other size
of fractional seconds such as milliseconds to a timestamp by specifying
a value with decimal positions.
%SECONDS(.000005) and %MSECONDS(5) both represent 5 microseconds.
%SECONDS(.123) represents 123 milliseconds.
See %SECONDS (Number of Seconds) for more information. 
For an example of date and time arithmetic operations, see Figure 1.
For more information, see Date Operations or Built-in Functions.