Create CountingMinutesI

Question:
Have the function CountingMinutesI(str) take the str parameter being passed which will be two times (each properly formatted with a colon and am or pm) separated by a hyphen and return the total number of minutes between the two times. The time will be in a 12 hour clock format. For example: if str is 9:00am-10:00am then the output should be 60. If str is 1:00pm-11:00am the output should be 1320.