Using variable for control chart sample size

[#1]

I am trying to use a variable for a control chart sample size and it won't accept it. The following code works:
Samples=6;
tempchart=Control Chart(
Sample Label( :DateTime ),
Sample Size( 4) ,
KSigma( 3 ),
Chart Col( :Value, XBar, R ),save summaries);

but these do not:
Samples=6;
tempchart=Control Chart(
Sample Label( :DateTime ),
Sample Size( Samples) ,
KSigma( 3 ),
Chart Col( :Value, XBar, R ),save summaries);

Samples=6;
tempchart=Control Chart(
Sample Label( :DateTime ),
Sample Size( 4*6) ,
KSigma( 3 ),
Chart Col( :Value, XBar, R ),save summaries);

I have also tried sample size (eval(Samples)), but it doesn't work either.

Any ideas?

[#2]

I think this is a case where only literals are accepted. See my answer to

http://communities.sas.com/thread/30007?tstart=0

for a work-around.

[#3]

Thanks for the post.  I am still having problems with this.  It looks like it is working correctly, but then the output is wrong.  If I run the following script:

XBar_R_BL = 4;

TempChartExp=substitute(expr(Control Chart(

  Sample Label( :DateTime ),

  Sample Size( SAMPLESIZESUB1) ,

  KSigma( 3 ),

  Chart Col( :Value, XBar, R ),save summaries)),expr(SAMPLESIZESUB1),XBar_R_BL);

show(TempChartExp);

TempChart1 = eval (TempChartExp);

The show statement gives the following:

     TempChartExp = Control Chart(Sample Label(:DateTime), Sample Size(4), KSigma(3), Chart Col(:Value, XBar, R), save summaries);

Which is exactly what I wanted.  However, when the eval statement is executed, I get a data table with 1 row and a chart with one point.  If I copy the script from the chart, I get:

Control Chart( Sample Label( :c000004 ), KSigma( 3 ), Chart Col( :Value, XBar, R ) )

So it has changed the column for the sample label and it has dropped the sample size al together.  Any help is appreciated.