Try either:
1.
myfield = name of field to search
SELE * FROM mydbf WHERE &myfield >0
2.
myExp =' myfield>9999'
SELE * FROM mydbf WHERE EVAL(myExp)

There was an article in FP Advisor couple of months ago I think by Tamar that illustrates the diff. between macro substitution, using () and Eval. Check it out.