Use scan twice

Hi! I'd like to generate a couple of processes with the Z' boson, giving different masses to the Z'. For this I use:

Set MZp scan:[1,2,3]

For each mass, there is a different corresponding width, according to a formula. If I use:

Set WZp scan:[value1, value2, value3]

it generates all combinations possible (so 3x3). If I use:

Set WZp sqrt(MZp)/pi + 0.01**2 (this is not the formula but it includes the operations used)

I get the WARNING: invalid set command param_card decay 26 (failed to identify LHA information).

Do you know how I can set the width correctly?
is there a way to have variables and functions in madgraph?

Thank you very much!