R help - Apr 2006 - parsing arguments of a function

Hi,
 
I have a simple problem writing a function that is to be called like
 
Myfunction( Column1 = low, Column2 = high, Column3 = all, Column4 = all,
data = mydata)
{.
contourplot(z ~ mydata$Column3* mydata$Column3)
.
}
 
Where Column1 and Column1 are the names of the dataframe mydata.
How do I parse the arguments to obtain both, name and value of the
argument.
I tried strsplit(Column1, "=") which gives me two strings but then I
fail to access the the corresponding columns of the dataframe with what
I get. I also tried eval(parse(text = .)) but it wont work. What am I
doing wrong. Please, somebody must have done something like that before.
I'm thankful for any hint.
 
Greetings

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