how to i approach this problem in Matlab

Prompts the user to enter a vector of 4 Threshold values ranging from 1 -100. This should be a single input statement where the user is expected to enter four values enclosed in square brackets.

If the user enters an invalid value in the Threshold vector or the Threshold vector doesnt have exactly four values, the script continues to prompt the user for a valid values and valid length until the user finally manages to follow directions