Some additional information would be helpful.
1.) What version of php
2.) What is MHz
On lines 14 and 15 it appears as though your variable declarations are incorrect.
I do not understand the necessity of MHz.
You can try this:
$Frequency = $HTTP_POST_VARS["Frequency MHz"];
$Range = $HTTP_POST_VARS["MHZ Range"];
If you are trying to instantiate a class (that you created), then the proper declaration in php looks like this:
$objectName = new nameOfClass(arg1,arg2,etc...);
I can help you further if you can give me a little bit more background on what you're trying to accomplish. Hope this helps.