Maths Expressions across tables

[BlakeHammond]

Hi
I’m trying to do a cross table maths expression. Expression using is " ([Installation Hours]*Rates[Markup labour Base Rate])".

But I get error Arithmetic expression ‘([Installation Hours]*Rates[Markup Labour Base Rate])’ has inputs of an invalid type ‘Unknown’

Unit Total Column which is where the above expression is going is - Type Number.

Markup Labour Base Rate - Type is Percent

Any help would be much appreciated.

Thanks

Blake