Question: How to create Action in Maplet with 'for - do' command

I try to use command "for a in 1,2 do Tangent(f, x = a) end do" in my Maplet but it does not work. 

Here it is:

 [Button("Tangent line", Action( Evaluate(for a in 'solve(diff(func, x) = slp, x)' do 'MMLV1'='MathML[Export]('y'=Tangent(func,x=a))' end do)))],

And here is all code for my Maplet

> restart:with(Maplets[Elements]):with(Student[Calculus1]):  TL2:=Maplet([ ["Input function  f(x)=", TextField['func'](20)],[Button("Display function",Action(Evaluate('MMLV'='MathML[Export](func)')))],MathMLViewer['MMLV'](), ["Input slope", TextField['slp'](10)],  [Button("Tangent line", Action( Evaluate(for a in 'solve(diff(func, x) = slp, x)' do 'MMLV1'='MathML[Export]('y'=Tangent(func,x=a))' end do)))],   MathMLViewer['MMLV1']()   ]):  Maplets[Display](TL2):
print(`output redirected...`); # input placeholder