Hello Howard:

This formula will return the time value of a three digit or for digit number using
the military time format without having to enter ( : ) between the numbers.

=IF(LEN(A1)=3,TIME(LEFT(A1,1),RIGHT(A1,2),0),IF(LEN(A1)=4,TIME(LEFT(A1,2),RIGHT(A1,2),0),A1))

Remember to format cell to a time format.

Example:

743 = 7:43 AM

1630 = 4:30 PM

Will also accommodate for entering time from the computers clock by pressing,
( Ctrl + Shift + ; ), then Enter.

Matt