Don't worry, I have found 2 solutions, the first being the simplest:
Data DataOut (Drop = i);
Set DataIn;
array Char(*) _Character_;
do i = 1 to dim(Char);
VarEntry = Char(i);
If substr(VarEntry, 1, 3) = 'Low' Then Char(i) = '-99'||Char(i);
End;
Run;
Or
%global vartype ;
%macro VARTYPE ( SASDSN, SASVAR );
%let dsid = %sysfunc( open ( &SASDSN,i) );
%let varnum = %sysfunc( varnum ( &dsid, &sasvar ) );
%let vartype = %sysfunc( vartype(&dsid, &varnum) );
%let rc = %sysfunc( close ( &dsid ) );
%mend VARTYPE;
*** Sample Call;
***%vartype( cpmsas.cpm10x, ml );
/*** end of sas program - vartype ***/