Formula: Start new number where last number stops in a range

Would like a formula to start a new number where the last number ends in a range. The number that will change from time to time is Ticket Serial Number. The ticket number is entered in cell A2 and B2 and concatenated in cell E2 (for example, 6723 - 238-248).

Ticket #: 6723 - (238-242)

I. when you entered a text value in A5, the ticket number is entered in B5.
For example,
A5: Baseball, B5: 6723-238
A6: Baseball, B6: 6723-239
A7: Baseball, B7: 6723-240
A8: Baseball, B8: 6723-241
A9: Baseball, B9: 6723-242

II. With the ticket range exhausted, a new ticket number is entered in A2 and B2. Goal is to have the new ticket number start below A9 (that is A10)
A2: 4567 - (501-505)

A10: Baseball, B10: 4567-501
A11: Baseball, B11: 4567-502
A12: Baseball, B12: 4567-503
A13: Baseball, B13: 4567-504
A14: Baseball, B14: 4567-505

Sample file attached.