Percentage chance to hit target number

Hi all -

Here is my spreadsheet:

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What I need to do is calculate in column F the percentage chance of someone rolling a 20 sided die and achieving a number greater than or equal to the number in column E after adding the bonus on the same line in column C. So for example, in order to get at least 18, as shown on line 5, the player would need to roll X+7.

What I THINK needs to happen is have excel check C5+H3,C5+H4,...C5+H22, determine how many "Yes this roll plus the modifier in column C will be equal to or greater than 18" there are, and then divide by 20. That's how it will seem to work in my mind at least.

The percent chance of success is capped at 95%, so even if all 20 rolls would beat the number in column E, there is still a 5% chance of failure.

I will be changing the numbers in columns C and E frequently as the situation changes.

Thank you in advance for any insight you can provide. I'll be checking regularly if you need more information or clarification from me.