If Error on 'Type Mismatch'

I am running a VBA userform that takes data input by the user and outputs a calculated value. If the user does not put in all of the required data, the calculation cannot be perfomed, and excel will return #Value instead of an actual calculated value. When my VBA userform wants to recall this calculated value to display on the userform, I get an error:

Run-time error ‘-2147352571 (80020005)’:

Could not set the Value property. Type Mismatch.

I understand why this error occurs. My vba userform is trying to pull in a value from a spreadsheet and instead it gets #Value. These types do not match. What I would like to do is if this error occurs, a pop up would occur on my userform stating "Please enter all required information." How would I execute this If Error statement? Also, these values I am displaying are called RefundFee and ProcessingFee. Thank you for your help, I do not have much experience with If Error statements.

Below is my Userform Code:

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