I'm assuming the OP is referring to UC2843, not UC2834 (which doesn't have a COMP pin)
Generally I only overdrive if the error amplifier is an OTA with a high output impedance. That's not the case for the UC2843. The datasheet does say the COMP pin has limited source and sink current, and mentions pulling COMP low to force PWM to shut off.
View attachment 194564
But it doesn't mention overriding COMP for any other purpose. It might work, but should be tested carefully.