I think you don't need to use interrupt for your case. You can use a simple logic in a common FC called by OB1. Interrupts in high speed input we use where the input signal is fast and short, The High speed input support 100Khz, a common input support 5 Khz. Inturrputs we use when the cycle scan is too long and you want a high speed reaction time example Less then 5 ms, because the plc stop the main program to execute the interrupt, then return to the main program.

Regards

I forgot the minute conversion.