Macro to choose which formula to use.

Basically I need to have a macro fill in a formula based on if a value exists.

So for this example cell M2 contains the following formula:

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And cell N2 contains the following formula:

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What I need is someway to check if $J$2-d2 >2

Cell L2 contains the difference between the employees time and the average shift length. (which would be the number 2 after the > in the example above)

If there would be anyway of making the number 2 variable with the use of a text box or something that would be even better.