dynamically set fit parameters and models with FindFit

I want to fit a gaussian profile by setting some values dynamically, but FindFit returns an error and i can't see the problem.

with a given gaussian:

gauss = Table[{x,
E^(-((x - 10)^2/(2 3^2))) + RandomReal[{-0.05, 0.05}]}, {x, 0, 20,
0.05}];

I set the model to:

gaussmodel = b Exp[-((x - d)^2/(2 g^2))];

With fitparameters set non-dynamically everything is fine:

fit = FindFit[gauss, gaussmodel, {{b, 1}, {d, 10}, {g, 3}}, x]
(*{b -> 1.00439, d -> 10.0109, g -> 2.9804}*)

Now I want to set the startingvalues as following:

InputField[Dynamic[startvalueb], Number]
InputField[Dynamic[startvalued], Number]
InputField[Dynamic[startvalueg], Number]
Checkbox[Dynamic[bool1]]

xx0 = {Dynamic[
Which[bool1 == True, {b, Dynamic[startvalueb]}, bool1 == False,
Null]], Dynamic[
Which[bool1 == True, {d, Dynamic[startvalued]}, bool1 == False,
Null]], Dynamic[
Which[bool1 == True, {g, Dynamic[startvalueg]}, bool1 == False,
Null]]}

witch returns just the form I need, but maybe not??!? Anyway

fi2 = FindFit[gauss, gaussmodel, xx0, x]

returns the following error:

FindFit::vloc:The variable {b,1} cannot be localized so that it can be assigned to numerical values.>>

What can I do to fix this?

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