apply in equation from fitting curve automatic

can any one help me how can i get this fitting curve equation automatic and apply in it
Uknow value is In(X)

Please note that this equation not constant As cell B14 , C14 which get from equation on curve , they can change wih any change in value A2:A8,B2:B8

please not understand what you mean
and i would like to know if m and b value will be get automatic or must be enter every time

Hi

To find m and b in your formula y=m.ln(x)+b try this formulas
for m

Formula:

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for b

Formula:

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Don't use in that formulas (A2, B2)