Mathematics function references

Hi,

I hope someone can help me here. 

I am making a simple machine to combine two liquids, a solvent and a type of adhesive, and want to use a logo8 + TDE to calculate and display the mix ratio.

There are flow meters on each liquid which provide a pulse, corresponding to a certain amount of liquid.

I need to determine the frequency of the pulses and calculate the flow rate, in mililitres/minute, for both liquids. Then perform another calculation to determine the ratio.

I will then manually adjust the pumps to achieve the correct proportions.

However the mathematics instruction won't accept the pulse frequency in the calculation, so I can't get beyond this point. 

My program is attached. I must be doing something wrong but I'm totally stuck!

How should I be doing this?

Thanks! 

Tom.

Look here:

https://support.industry.siemens.com/cs/document/109471094/how-can-you-configure-references-between-blocks-in-logo!-8?dti=0&pnid=13617&lc=en-DE