Conditional formatting depending on another cell

Hello,

Here is what I have:

Cell A1 is the motor size in tones = user enters a decimal number between 0.001 to 1000

Cell A2 = a drop down list of 6 different motor names/sizes, e.g.:

MotorName1<5 tones
MotorName2<5 tones
15 tones>MotorName3>5 tones
30 tones>MotorName5>15 tones
...
...

This drop down list of 6 different motor names/sizes is random and it's really just a text (not a mathematical formula, or number based). However, I do not have the freedom to change the naming of the drop down list to make it more mathematical since it comes from a standard used in the industry.

I need Cell A1 because the value the user enters is used in some mathematical formula. I need Cell A2 to have an idea what category of motors the user is using; it's just text information that will be saved in a data base.

Here is what I want to do:

If say the user selected in A2: MotorName1<5 tones, and he entered 6 tones in A1, and since 6 tones is bigger than 5 tones then I want A1 to be visually flagged by changing the cell's format (changing the cell colour to red or changing the cell's border to red, or something like that). Or even better, having a stop message pop up telling the user he must enter a value <5 because that's the category he selected in A2.

How do I do that?

Thank you very much in advance and I am looking forward to your replies

Posting a sample workbork would help. As we'll need to know your exact sytax of the list.

Thanks a lot. I've attached a sample file.

Pump, please!