Validating a String Using a While Loop

I'm stuck in what seems to be an infinite loop while trying to validate an input string. Even if I enter V or C it still displays the "error".

 % INPUT user choice for calculating voltage or current
choice = input('\nPlease enter V to calculate volts or C to calculate current: ', 's');

 % TEST if user entered V or C
while choice ~= 'v' || choice ~= 'V' || choice ~= 'c' || choice ~= 'C'
    choice = input('ERROR! Please enter either V or C: ', 's');
end

I'm relatively new to MATLAB so I apologize in advance if it is messy or not the most efficient way to do this. Any ideas or suggestions?

Answer 1

[Walter Roberson]

while ~ismember(choice, 'vcVC')
  choice = input('ERROR! Please enter either V or C: ', 's');
end

Or

while choice ~= 'v' && choice ~= 'V' && choice ~= 'c' && choice ~= 'C'
  choice = input('ERROR! Please enter either V or C: ', 's');
end

or

while ~(choice == 'v' || choice == 'V' || choice == 'c' || choice == 'C')
  choice = input('ERROR! Please enter either V or C: ', 's');
end