[R] Evaluating expresssions as parameter values

[Erich Neuwirth]

I need to play games with an expression similar to the following one:

print(xyplot(DepVar ~ Group|Covar, groups=Othergroup,
	data=mydf, pch = 18 ,main="Testcase",auto.key = TRUE))


The problem is that  the formula argument (the first argument)
an the groups argument are passed over from another program as strings.

The formula argument does not pose problems,
I can do as.formula("DepVar ~ Group|Covar")
bit I could not find an equivalent technique for the groups parameter.
as.expression(... does not work and neither does
parse(text=...

Is there a way of accomplishing what I need?