Dynamically locking a cell depending upon value of another cell.
 

I have a sheet set up as follows:-

Columns A to I.

Columns A, B and C (C is actually hidden) are populated by keying in data in
column D and a Vlookup refereeing to another sheet being used. Also note that
the column A, B and C are LOCKED.

Column E is unlocked and data is entered.

Column F is a formula that checks the individual row and compares the value
in column C against column E, if they match it displays YES in column F, if
they dont match it displays Mis Match in column F, obviously this occurs as
soon as either enter ot tab are depressed on the keyboard. Please note column
F is locked as it has a formula in it.

What I am trying to achieve is that if a column F says Mis Match, then input
should not be allowed in column G, and I want to automatically lock column G,
in the appropriate row.

Additionally, if this can be done, I do not want the code to be visible.

Any assistance offered would be most appreciated.